lunr/lunr.js

Simple full-text search in your browser.

/**
 * lunr - http://lunrjs.com - A bit like Solr, but much smaller and not as bright - 2.3.9
 * Copyright (C) 2020 Oliver Nightingale
 * @license MIT
 */

;(function(){

/**
 * A convenience function for configuring and constructing
 * a new lunr Index.
 *
 * A lunr.Builder instance is created and the pipeline setup
 * with a trimmer, stop word filter and stemmer.
 *
 * This builder object is yielded to the configuration function
 * that is passed as a parameter, allowing the list of fields
 * and other builder parameters to be customised.
 *
 * All documents _must_ be added within the passed config function.
 *
 * @example
 * var idx = lunr(function () {
 *   this.field('title')
 *   this.field('body')
 *   this.ref('id')
 *
 *   documents.forEach(function (doc) {
 *     this.add(doc)
 *   }, this)
 * })
 *
 * @see {@link lunr.Builder}
 * @see {@link lunr.Pipeline}
 * @see {@link lunr.trimmer}
 * @see {@link lunr.stopWordFilter}
 * @see {@link lunr.stemmer}
 * @namespace {function} lunr
 */
var lunr = function (config) {
  var builder = new lunr.Builder

  builder.pipeline.add(
    lunr.trimmer,
    lunr.stopWordFilter,
    lunr.stemmer
  )

  builder.searchPipeline.add(
    lunr.stemmer
  )

  config.call(builder, builder)
  return builder.build()
}

lunr.version = "2.3.9"
/*!
 * lunr.utils
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * A namespace containing utils for the rest of the lunr library
 * @namespace lunr.utils
 */
lunr.utils = {}

/**
 * Print a warning message to the console.
 *
 * @param {String} message The message to be printed.
 * @memberOf lunr.utils
 * @function
 */
lunr.utils.warn = (function (global) {
  /* eslint-disable no-console */
  return function (message) {
    if (global.console && console.warn) {
      console.warn(message)
    }
  }
  /* eslint-enable no-console */
})(this)

/**
 * Convert an object to a string.
 *
 * In the case of `null` and `undefined` the function returns
 * the empty string, in all other cases the result of calling
 * `toString` on the passed object is returned.
 *
 * @param {Any} obj The object to convert to a string.
 * @return {String} string representation of the passed object.
 * @memberOf lunr.utils
 */
lunr.utils.asString = function (obj) {
  if (obj === void 0 || obj === null) {
    return ""
  } else {
    return obj.toString()
  }
}

/**
 * Clones an object.
 *
 * Will create a copy of an existing object such that any mutations
 * on the copy cannot affect the original.
 *
 * Only shallow objects are supported, passing a nested object to this
 * function will cause a TypeError.
 *
 * Objects with primitives, and arrays of primitives are supported.
 *
 * @param {Object} obj The object to clone.
 * @return {Object} a clone of the passed object.
 * @throws {TypeError} when a nested object is passed.
 * @memberOf Utils
 */
lunr.utils.clone = function (obj) {
  if (obj === null || obj === undefined) {
    return obj
  }

  var clone = Object.create(null),
      keys = Object.keys(obj)

  for (var i = 0; i < keys.length; i++) {
    var key = keys[i],
        val = obj[key]

    if (Array.isArray(val)) {
      clone[key] = val.slice()
      continue
    }

    if (typeof val === 'string' ||
        typeof val === 'number' ||
        typeof val === 'boolean') {
      clone[key] = val
      continue
    }

    throw new TypeError("clone is not deep and does not support nested objects")
  }

  return clone
}
lunr.FieldRef = function (docRef, fieldName, stringValue) {
  this.docRef = docRef
  this.fieldName = fieldName
  this._stringValue = stringValue
}

lunr.FieldRef.joiner = "/"

lunr.FieldRef.fromString = function (s) {
  var n = s.indexOf(lunr.FieldRef.joiner)

  if (n === -1) {
    throw "malformed field ref string"
  }

  var fieldRef = s.slice(0, n),
      docRef = s.slice(n + 1)

  return new lunr.FieldRef (docRef, fieldRef, s)
}

lunr.FieldRef.prototype.toString = function () {
  if (this._stringValue == undefined) {
    this._stringValue = this.fieldName + lunr.FieldRef.joiner + this.docRef
  }

  return this._stringValue
}
/*!
 * lunr.Set
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * A lunr set.
 *
 * @constructor
 */
lunr.Set = function (elements) {
  this.elements = Object.create(null)

  if (elements) {
    this.length = elements.length

    for (var i = 0; i < this.length; i++) {
      this.elements[elements[i]] = true
    }
  } else {
    this.length = 0
  }
}

/**
 * A complete set that contains all elements.
 *
 * @static
 * @readonly
 * @type {lunr.Set}
 */
lunr.Set.complete = {
  intersect: function (other) {
    return other
  },

  union: function () {
    return this
  },

  contains: function () {
    return true
  }
}

/**
 * An empty set that contains no elements.
 *
 * @static
 * @readonly
 * @type {lunr.Set}
 */
lunr.Set.empty = {
  intersect: function () {
    return this
  },

  union: function (other) {
    return other
  },

  contains: function () {
    return false
  }
}

/**
 * Returns true if this set contains the specified object.
 *
 * @param {object} object - Object whose presence in this set is to be tested.
 * @returns {boolean} - True if this set contains the specified object.
 */
lunr.Set.prototype.contains = function (object) {
  return !!this.elements[object]
}

/**
 * Returns a new set containing only the elements that are present in both
 * this set and the specified set.
 *
 * @param {lunr.Set} other - set to intersect with this set.
 * @returns {lunr.Set} a new set that is the intersection of this and the specified set.
 */

lunr.Set.prototype.intersect = function (other) {
  var a, b, elements, intersection = []

  if (other === lunr.Set.complete) {
    return this
  }

  if (other === lunr.Set.empty) {
    return other
  }

  if (this.length < other.length) {
    a = this
    b = other
  } else {
    a = other
    b = this
  }

  elements = Object.keys(a.elements)

  for (var i = 0; i < elements.length; i++) {
    var element = elements[i]
    if (element in b.elements) {
      intersection.push(element)
    }
  }

  return new lunr.Set (intersection)
}

/**
 * Returns a new set combining the elements of this and the specified set.
 *
 * @param {lunr.Set} other - set to union with this set.
 * @return {lunr.Set} a new set that is the union of this and the specified set.
 */

lunr.Set.prototype.union = function (other) {
  if (other === lunr.Set.complete) {
    return lunr.Set.complete
  }

  if (other === lunr.Set.empty) {
    return this
  }

  return new lunr.Set(Object.keys(this.elements).concat(Object.keys(other.elements)))
}
/**
 * A function to calculate the inverse document frequency for
 * a posting. This is shared between the builder and the index
 *
 * @private
 * @param {object} posting - The posting for a given term
 * @param {number} documentCount - The total number of documents.
 */
lunr.idf = function (posting, documentCount) {
  var documentsWithTerm = 0

  for (var fieldName in posting) {
    if (fieldName == '_index') continue // Ignore the term index, its not a field
    documentsWithTerm += Object.keys(posting[fieldName]).length
  }

  var x = (documentCount - documentsWithTerm + 0.5) / (documentsWithTerm + 0.5)

  return Math.log(1 + Math.abs(x))
}

/**
 * A token wraps a string representation of a token
 * as it is passed through the text processing pipeline.
 *
 * @constructor
 * @param {string} [str=''] - The string token being wrapped.
 * @param {object} [metadata={}] - Metadata associated with this token.
 */
lunr.Token = function (str, metadata) {
  this.str = str || ""
  this.metadata = metadata || {}
}

/**
 * Returns the token string that is being wrapped by this object.
 *
 * @returns {string}
 */
lunr.Token.prototype.toString = function () {
  return this.str
}

/**
 * A token update function is used when updating or optionally
 * when cloning a token.
 *
 * @callback lunr.Token~updateFunction
 * @param {string} str - The string representation of the token.
 * @param {Object} metadata - All metadata associated with this token.
 */

/**
 * Applies the given function to the wrapped string token.
 *
 * @example
 * token.update(function (str, metadata) {
 *   return str.toUpperCase()
 * })
 *
 * @param {lunr.Token~updateFunction} fn - A function to apply to the token string.
 * @returns {lunr.Token}
 */
lunr.Token.prototype.update = function (fn) {
  this.str = fn(this.str, this.metadata)
  return this
}

/**
 * Creates a clone of this token. Optionally a function can be
 * applied to the cloned token.
 *
 * @param {lunr.Token~updateFunction} [fn] - An optional function to apply to the cloned token.
 * @returns {lunr.Token}
 */
lunr.Token.prototype.clone = function (fn) {
  fn = fn || function (s) { return s }
  return new lunr.Token (fn(this.str, this.metadata), this.metadata)
}
/*!
 * lunr.tokenizer
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * A function for splitting a string into tokens ready to be inserted into
 * the search index. Uses `lunr.tokenizer.separator` to split strings, change
 * the value of this property to change how strings are split into tokens.
 *
 * This tokenizer will convert its parameter to a string by calling `toString` and
 * then will split this string on the character in `lunr.tokenizer.separator`.
 * Arrays will have their elements converted to strings and wrapped in a lunr.Token.
 *
 * Optional metadata can be passed to the tokenizer, this metadata will be cloned and
 * added as metadata to every token that is created from the object to be tokenized.
 *
 * @static
 * @param {?(string|object|object[])} obj - The object to convert into tokens
 * @param {?object} metadata - Optional metadata to associate with every token
 * @returns {lunr.Token[]}
 * @see {@link lunr.Pipeline}
 */
lunr.tokenizer = function (obj, metadata) {
  if (obj == null || obj == undefined) {
    return []
  }

  if (Array.isArray(obj)) {
    return obj.map(function (t) {
      return new lunr.Token(
        lunr.utils.asString(t).toLowerCase(),
        lunr.utils.clone(metadata)
      )
    })
  }

  var str = obj.toString().toLowerCase(),
      len = str.length,
      tokens = []

  for (var sliceEnd = 0, sliceStart = 0; sliceEnd <= len; sliceEnd++) {
    var char = str.charAt(sliceEnd),
        sliceLength = sliceEnd - sliceStart

    if ((char.match(lunr.tokenizer.separator) || sliceEnd == len)) {

      if (sliceLength > 0) {
        var tokenMetadata = lunr.utils.clone(metadata) || {}
        tokenMetadata["position"] = [sliceStart, sliceLength]
        tokenMetadata["index"] = tokens.length

        tokens.push(
          new lunr.Token (
            str.slice(sliceStart, sliceEnd),
            tokenMetadata
          )
        )
      }

      sliceStart = sliceEnd + 1
    }

  }

  return tokens
}

/**
 * The separator used to split a string into tokens. Override this property to change the behaviour of
 * `lunr.tokenizer` behaviour when tokenizing strings. By default this splits on whitespace and hyphens.
 *
 * @static
 * @see lunr.tokenizer
 */
lunr.tokenizer.separator = /[\s\-]+/
/*!
 * lunr.Pipeline
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * lunr.Pipelines maintain an ordered list of functions to be applied to all
 * tokens in documents entering the search index and queries being ran against
 * the index.
 *
 * An instance of lunr.Index created with the lunr shortcut will contain a
 * pipeline with a stop word filter and an English language stemmer. Extra
 * functions can be added before or after either of these functions or these
 * default functions can be removed.
 *
 * When run the pipeline will call each function in turn, passing a token, the
 * index of that token in the original list of all tokens and finally a list of
 * all the original tokens.
 *
 * The output of functions in the pipeline will be passed to the next function
 * in the pipeline. To exclude a token from entering the index the function
 * should return undefined, the rest of the pipeline will not be called with
 * this token.
 *
 * For serialisation of pipelines to work, all functions used in an instance of
 * a pipeline should be registered with lunr.Pipeline. Registered functions can
 * then be loaded. If trying to load a serialised pipeline that uses functions
 * that are not registered an error will be thrown.
 *
 * If not planning on serialising the pipeline then registering pipeline functions
 * is not necessary.
 *
 * @constructor
 */
lunr.Pipeline = function () {
  this._stack = []
}

lunr.Pipeline.registeredFunctions = Object.create(null)

/**
 * A pipeline function maps lunr.Token to lunr.Token. A lunr.Token contains the token
 * string as well as all known metadata. A pipeline function can mutate the token string
 * or mutate (or add) metadata for a given token.
 *
 * A pipeline function can indicate that the passed token should be discarded by returning
 * null, undefined or an empty string. This token will not be passed to any downstream pipeline
 * functions and will not be added to the index.
 *
 * Multiple tokens can be returned by returning an array of tokens. Each token will be passed
 * to any downstream pipeline functions and all will returned tokens will be added to the index.
 *
 * Any number of pipeline functions may be chained together using a lunr.Pipeline.
 *
 * @interface lunr.PipelineFunction
 * @param {lunr.Token} token - A token from the document being processed.
 * @param {number} i - The index of this token in the complete list of tokens for this document/field.
 * @param {lunr.Token[]} tokens - All tokens for this document/field.
 * @returns {(?lunr.Token|lunr.Token[])}
 */

/**
 * Register a function with the pipeline.
 *
 * Functions that are used in the pipeline should be registered if the pipeline
 * needs to be serialised, or a serialised pipeline needs to be loaded.
 *
 * Registering a function does not add it to a pipeline, functions must still be
 * added to instances of the pipeline for them to be used when running a pipeline.
 *
 * @param {lunr.PipelineFunction} fn - The function to check for.
 * @param {String} label - The label to register this function with
 */
lunr.Pipeline.registerFunction = function (fn, label) {
  if (label in this.registeredFunctions) {
    lunr.utils.warn('Overwriting existing registered function: ' + label)
  }

  fn.label = label
  lunr.Pipeline.registeredFunctions[fn.label] = fn
}

/**
 * Warns if the function is not registered as a Pipeline function.
 *
 * @param {lunr.PipelineFunction} fn - The function to check for.
 * @private
 */
lunr.Pipeline.warnIfFunctionNotRegistered = function (fn) {
  var isRegistered = fn.label && (fn.label in this.registeredFunctions)

  if (!isRegistered) {
    lunr.utils.warn('Function is not registered with pipeline. This may cause problems when serialising the index.\n', fn)
  }
}

/**
 * Loads a previously serialised pipeline.
 *
 * All functions to be loaded must already be registered with lunr.Pipeline.
 * If any function from the serialised data has not been registered then an
 * error will be thrown.
 *
 * @param {Object} serialised - The serialised pipeline to load.
 * @returns {lunr.Pipeline}
 */
lunr.Pipeline.load = function (serialised) {
  var pipeline = new lunr.Pipeline

  serialised.forEach(function (fnName) {
    var fn = lunr.Pipeline.registeredFunctions[fnName]

    if (fn) {
      pipeline.add(fn)
    } else {
      throw new Error('Cannot load unregistered function: ' + fnName)
    }
  })

  return pipeline
}

/**
 * Adds new functions to the end of the pipeline.
 *
 * Logs a warning if the function has not been registered.
 *
 * @param {lunr.PipelineFunction[]} functions - Any number of functions to add to the pipeline.
 */
lunr.Pipeline.prototype.add = function () {
  var fns = Array.prototype.slice.call(arguments)

  fns.forEach(function (fn) {
    lunr.Pipeline.warnIfFunctionNotRegistered(fn)
    this._stack.push(fn)
  }, this)
}

/**
 * Adds a single function after a function that already exists in the
 * pipeline.
 *
 * Logs a warning if the function has not been registered.
 *
 * @param {lunr.PipelineFunction} existingFn - A function that already exists in the pipeline.
 * @param {lunr.PipelineFunction} newFn - The new function to add to the pipeline.
 */
lunr.Pipeline.prototype.after = function (existingFn, newFn) {
  lunr.Pipeline.warnIfFunctionNotRegistered(newFn)

  var pos = this._stack.indexOf(existingFn)
  if (pos == -1) {
    throw new Error('Cannot find existingFn')
  }

  pos = pos + 1
  this._stack.splice(pos, 0, newFn)
}

/**
 * Adds a single function before a function that already exists in the
 * pipeline.
 *
 * Logs a warning if the function has not been registered.
 *
 * @param {lunr.PipelineFunction} existingFn - A function that already exists in the pipeline.
 * @param {lunr.PipelineFunction} newFn - The new function to add to the pipeline.
 */
lunr.Pipeline.prototype.before = function (existingFn, newFn) {
  lunr.Pipeline.warnIfFunctionNotRegistered(newFn)

  var pos = this._stack.indexOf(existingFn)
  if (pos == -1) {
    throw new Error('Cannot find existingFn')
  }

  this._stack.splice(pos, 0, newFn)
}

/**
 * Removes a function from the pipeline.
 *
 * @param {lunr.PipelineFunction} fn The function to remove from the pipeline.
 */
lunr.Pipeline.prototype.remove = function (fn) {
  var pos = this._stack.indexOf(fn)
  if (pos == -1) {
    return
  }

  this._stack.splice(pos, 1)
}

/**
 * Runs the current list of functions that make up the pipeline against the
 * passed tokens.
 *
 * @param {Array} tokens The tokens to run through the pipeline.
 * @returns {Array}
 */
lunr.Pipeline.prototype.run = function (tokens) {
  var stackLength = this._stack.length

  for (var i = 0; i < stackLength; i++) {
    var fn = this._stack[i]
    var memo = []

    for (var j = 0; j < tokens.length; j++) {
      var result = fn(tokens[j], j, tokens)

      if (result === null || result === void 0 || result === '') continue

      if (Array.isArray(result)) {
        for (var k = 0; k < result.length; k++) {
          memo.push(result[k])
        }
      } else {
        memo.push(result)
      }
    }

    tokens = memo
  }

  return tokens
}

/**
 * Convenience method for passing a string through a pipeline and getting
 * strings out. This method takes care of wrapping the passed string in a
 * token and mapping the resulting tokens back to strings.
 *
 * @param {string} str - The string to pass through the pipeline.
 * @param {?object} metadata - Optional metadata to associate with the token
 * passed to the pipeline.
 * @returns {string[]}
 */
lunr.Pipeline.prototype.runString = function (str, metadata) {
  var token = new lunr.Token (str, metadata)

  return this.run([token]).map(function (t) {
    return t.toString()
  })
}

/**
 * Resets the pipeline by removing any existing processors.
 *
 */
lunr.Pipeline.prototype.reset = function () {
  this._stack = []
}

/**
 * Returns a representation of the pipeline ready for serialisation.
 *
 * Logs a warning if the function has not been registered.
 *
 * @returns {Array}
 */
lunr.Pipeline.prototype.toJSON = function () {
  return this._stack.map(function (fn) {
    lunr.Pipeline.warnIfFunctionNotRegistered(fn)

    return fn.label
  })
}
/*!
 * lunr.Vector
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * A vector is used to construct the vector space of documents and queries. These
 * vectors support operations to determine the similarity between two documents or
 * a document and a query.
 *
 * Normally no parameters are required for initializing a vector, but in the case of
 * loading a previously dumped vector the raw elements can be provided to the constructor.
 *
 * For performance reasons vectors are implemented with a flat array, where an elements
 * index is immediately followed by its value. E.g. [index, value, index, value]. This
 * allows the underlying array to be as sparse as possible and still offer decent
 * performance when being used for vector calculations.
 *
 * @constructor
 * @param {Number[]} [elements] - The flat list of element index and element value pairs.
 */
lunr.Vector = function (elements) {
  this._magnitude = 0
  this.elements = elements || []
}


/**
 * Calculates the position within the vector to insert a given index.
 *
 * This is used internally by insert and upsert. If there are duplicate indexes then
 * the position is returned as if the value for that index were to be updated, but it
 * is the callers responsibility to check whether there is a duplicate at that index
 *
 * @param {Number} insertIdx - The index at which the element should be inserted.
 * @returns {Number}
 */
lunr.Vector.prototype.positionForIndex = function (index) {
  // For an empty vector the tuple can be inserted at the beginning
  if (this.elements.length == 0) {
    return 0
  }

  var start = 0,
      end = this.elements.length / 2,
      sliceLength = end - start,
      pivotPoint = Math.floor(sliceLength / 2),
      pivotIndex = this.elements[pivotPoint * 2]

  while (sliceLength > 1) {
    if (pivotIndex < index) {
      start = pivotPoint
    }

    if (pivotIndex > index) {
      end = pivotPoint
    }

    if (pivotIndex == index) {
      break
    }

    sliceLength = end - start
    pivotPoint = start + Math.floor(sliceLength / 2)
    pivotIndex = this.elements[pivotPoint * 2]
  }

  if (pivotIndex == index) {
    return pivotPoint * 2
  }

  if (pivotIndex > index) {
    return pivotPoint * 2
  }

  if (pivotIndex < index) {
    return (pivotPoint + 1) * 2
  }
}

/**
 * Inserts an element at an index within the vector.
 *
 * Does not allow duplicates, will throw an error if there is already an entry
 * for this index.
 *
 * @param {Number} insertIdx - The index at which the element should be inserted.
 * @param {Number} val - The value to be inserted into the vector.
 */
lunr.Vector.prototype.insert = function (insertIdx, val) {
  this.upsert(insertIdx, val, function () {
    throw "duplicate index"
  })
}

/**
 * Inserts or updates an existing index within the vector.
 *
 * @param {Number} insertIdx - The index at which the element should be inserted.
 * @param {Number} val - The value to be inserted into the vector.
 * @param {function} fn - A function that is called for updates, the existing value and the
 * requested value are passed as arguments
 */
lunr.Vector.prototype.upsert = function (insertIdx, val, fn) {
  this._magnitude = 0
  var position = this.positionForIndex(insertIdx)

  if (this.elements[position] == insertIdx) {
    this.elements[position + 1] = fn(this.elements[position + 1], val)
  } else {
    this.elements.splice(position, 0, insertIdx, val)
  }
}

/**
 * Calculates the magnitude of this vector.
 *
 * @returns {Number}
 */
lunr.Vector.prototype.magnitude = function () {
  if (this._magnitude) return this._magnitude

  var sumOfSquares = 0,
      elementsLength = this.elements.length

  for (var i = 1; i < elementsLength; i += 2) {
    var val = this.elements[i]
    sumOfSquares += val * val
  }

  return this._magnitude = Math.sqrt(sumOfSquares)
}

/**
 * Calculates the dot product of this vector and another vector.
 *
 * @param {lunr.Vector} otherVector - The vector to compute the dot product with.
 * @returns {Number}
 */
lunr.Vector.prototype.dot = function (otherVector) {
  var dotProduct = 0,
      a = this.elements, b = otherVector.elements,
      aLen = a.length, bLen = b.length,
      aVal = 0, bVal = 0,
      i = 0, j = 0

  while (i < aLen && j < bLen) {
    aVal = a[i], bVal = b[j]
    if (aVal < bVal) {
      i += 2
    } else if (aVal > bVal) {
      j += 2
    } else if (aVal == bVal) {
      dotProduct += a[i + 1] * b[j + 1]
      i += 2
      j += 2
    }
  }

  return dotProduct
}

/**
 * Calculates the similarity between this vector and another vector.
 *
 * @param {lunr.Vector} otherVector - The other vector to calculate the
 * similarity with.
 * @returns {Number}
 */
lunr.Vector.prototype.similarity = function (otherVector) {
  return this.dot(otherVector) / this.magnitude() || 0
}

/**
 * Converts the vector to an array of the elements within the vector.
 *
 * @returns {Number[]}
 */
lunr.Vector.prototype.toArray = function () {
  var output = new Array (this.elements.length / 2)

  for (var i = 1, j = 0; i < this.elements.length; i += 2, j++) {
    output[j] = this.elements[i]
  }

  return output
}

/**
 * A JSON serializable representation of the vector.
 *
 * @returns {Number[]}
 */
lunr.Vector.prototype.toJSON = function () {
  return this.elements
}
/* eslint-disable */
/*!
 * lunr.stemmer
 * Copyright (C) 2020 Oliver Nightingale
 * Includes code from - http://tartarus.org/~martin/PorterStemmer/js.txt
 */

/**
 * lunr.stemmer is an english language stemmer, this is a JavaScript
 * implementation of the PorterStemmer taken from http://tartarus.org/~martin
 *
 * @static
 * @implements {lunr.PipelineFunction}
 * @param {lunr.Token} token - The string to stem
 * @returns {lunr.Token}
 * @see {@link lunr.Pipeline}
 * @function
 */
lunr.stemmer = (function(){
  var step2list = {
      "ational" : "ate",
      "tional" : "tion",
      "enci" : "ence",
      "anci" : "ance",
      "izer" : "ize",
      "bli" : "ble",
      "alli" : "al",
      "entli" : "ent",
      "eli" : "e",
      "ousli" : "ous",
      "ization" : "ize",
      "ation" : "ate",
      "ator" : "ate",
      "alism" : "al",
      "iveness" : "ive",
      "fulness" : "ful",
      "ousness" : "ous",
      "aliti" : "al",
      "iviti" : "ive",
      "biliti" : "ble",
      "logi" : "log"
    },

    step3list = {
      "icate" : "ic",
      "ative" : "",
      "alize" : "al",
      "iciti" : "ic",
      "ical" : "ic",
      "ful" : "",
      "ness" : ""
    },

    c = "[^aeiou]",          // consonant
    v = "[aeiouy]",          // vowel
    C = c + "[^aeiouy]*",    // consonant sequence
    V = v + "[aeiou]*",      // vowel sequence

    mgr0 = "^(" + C + ")?" + V + C,               // [C]VC... is m>0
    meq1 = "^(" + C + ")?" + V + C + "(" + V + ")?$",  // [C]VC[V] is m=1
    mgr1 = "^(" + C + ")?" + V + C + V + C,       // [C]VCVC... is m>1
    s_v = "^(" + C + ")?" + v;                   // vowel in stem

  var re_mgr0 = new RegExp(mgr0);
  var re_mgr1 = new RegExp(mgr1);
  var re_meq1 = new RegExp(meq1);
  var re_s_v = new RegExp(s_v);

  var re_1a = /^(.+?)(ss|i)es$/;
  var re2_1a = /^(.+?)([^s])s$/;
  var re_1b = /^(.+?)eed$/;
  var re2_1b = /^(.+?)(ed|ing)$/;
  var re_1b_2 = /.$/;
  var re2_1b_2 = /(at|bl|iz)$/;
  var re3_1b_2 = new RegExp("([^aeiouylsz])\\1$");
  var re4_1b_2 = new RegExp("^" + C + v + "[^aeiouwxy]$");

  var re_1c = /^(.+?[^aeiou])y$/;
  var re_2 = /^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$/;

  var re_3 = /^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$/;

  var re_4 = /^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$/;
  var re2_4 = /^(.+?)(s|t)(ion)$/;

  var re_5 = /^(.+?)e$/;
  var re_5_1 = /ll$/;
  var re3_5 = new RegExp("^" + C + v + "[^aeiouwxy]$");

  var porterStemmer = function porterStemmer(w) {
    var stem,
      suffix,
      firstch,
      re,
      re2,
      re3,
      re4;

    if (w.length < 3) { return w; }

    firstch = w.substr(0,1);
    if (firstch == "y") {
      w = firstch.toUpperCase() + w.substr(1);
    }

    // Step 1a
    re = re_1a
    re2 = re2_1a;

    if (re.test(w)) { w = w.replace(re,"$1$2"); }
    else if (re2.test(w)) { w = w.replace(re2,"$1$2"); }

    // Step 1b
    re = re_1b;
    re2 = re2_1b;
    if (re.test(w)) {
      var fp = re.exec(w);
      re = re_mgr0;
      if (re.test(fp[1])) {
        re = re_1b_2;
        w = w.replace(re,"");
      }
    } else if (re2.test(w)) {
      var fp = re2.exec(w);
      stem = fp[1];
      re2 = re_s_v;
      if (re2.test(stem)) {
        w = stem;
        re2 = re2_1b_2;
        re3 = re3_1b_2;
        re4 = re4_1b_2;
        if (re2.test(w)) { w = w + "e"; }
        else if (re3.test(w)) { re = re_1b_2; w = w.replace(re,""); }
        else if (re4.test(w)) { w = w + "e"; }
      }
    }

    // Step 1c - replace suffix y or Y by i if preceded by a non-vowel which is not the first letter of the word (so cry -> cri, by -> by, say -> say)
    re = re_1c;
    if (re.test(w)) {
      var fp = re.exec(w);
      stem = fp[1];
      w = stem + "i";
    }

    // Step 2
    re = re_2;
    if (re.test(w)) {
      var fp = re.exec(w);
      stem = fp[1];
      suffix = fp[2];
      re = re_mgr0;
      if (re.test(stem)) {
        w = stem + step2list[suffix];
      }
    }

    // Step 3
    re = re_3;
    if (re.test(w)) {
      var fp = re.exec(w);
      stem = fp[1];
      suffix = fp[2];
      re = re_mgr0;
      if (re.test(stem)) {
        w = stem + step3list[suffix];
      }
    }

    // Step 4
    re = re_4;
    re2 = re2_4;
    if (re.test(w)) {
      var fp = re.exec(w);
      stem = fp[1];
      re = re_mgr1;
      if (re.test(stem)) {
        w = stem;
      }
    } else if (re2.test(w)) {
      var fp = re2.exec(w);
      stem = fp[1] + fp[2];
      re2 = re_mgr1;
      if (re2.test(stem)) {
        w = stem;
      }
    }

    // Step 5
    re = re_5;
    if (re.test(w)) {
      var fp = re.exec(w);
      stem = fp[1];
      re = re_mgr1;
      re2 = re_meq1;
      re3 = re3_5;
      if (re.test(stem) || (re2.test(stem) && !(re3.test(stem)))) {
        w = stem;
      }
    }

    re = re_5_1;
    re2 = re_mgr1;
    if (re.test(w) && re2.test(w)) {
      re = re_1b_2;
      w = w.replace(re,"");
    }

    // and turn initial Y back to y

    if (firstch == "y") {
      w = firstch.toLowerCase() + w.substr(1);
    }

    return w;
  };

  return function (token) {
    return token.update(porterStemmer);
  }
})();

lunr.Pipeline.registerFunction(lunr.stemmer, 'stemmer')
/*!
 * lunr.stopWordFilter
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * lunr.generateStopWordFilter builds a stopWordFilter function from the provided
 * list of stop words.
 *
 * The built in lunr.stopWordFilter is built using this generator and can be used
 * to generate custom stopWordFilters for applications or non English languages.
 *
 * @function
 * @param {Array} token The token to pass through the filter
 * @returns {lunr.PipelineFunction}
 * @see lunr.Pipeline
 * @see lunr.stopWordFilter
 */
lunr.generateStopWordFilter = function (stopWords) {
  var words = stopWords.reduce(function (memo, stopWord) {
    memo[stopWord] = stopWord
    return memo
  }, {})

  return function (token) {
    if (token && words[token.toString()] !== token.toString()) return token
  }
}

/**
 * lunr.stopWordFilter is an English language stop word list filter, any words
 * contained in the list will not be passed through the filter.
 *
 * This is intended to be used in the Pipeline. If the token does not pass the
 * filter then undefined will be returned.
 *
 * @function
 * @implements {lunr.PipelineFunction}
 * @params {lunr.Token} token - A token to check for being a stop word.
 * @returns {lunr.Token}
 * @see {@link lunr.Pipeline}
 */
lunr.stopWordFilter = lunr.generateStopWordFilter([
  'a',
  'able',
  'about',
  'across',
  'after',
  'all',
  'almost',
  'also',
  'am',
  'among',
  'an',
  'and',
  'any',
  'are',
  'as',
  'at',
  'be',
  'because',
  'been',
  'but',
  'by',
  'can',
  'cannot',
  'could',
  'dear',
  'did',
  'do',
  'does',
  'either',
  'else',
  'ever',
  'every',
  'for',
  'from',
  'get',
  'got',
  'had',
  'has',
  'have',
  'he',
  'her',
  'hers',
  'him',
  'his',
  'how',
  'however',
  'i',
  'if',
  'in',
  'into',
  'is',
  'it',
  'its',
  'just',
  'least',
  'let',
  'like',
  'likely',
  'may',
  'me',
  'might',
  'most',
  'must',
  'my',
  'neither',
  'no',
  'nor',
  'not',
  'of',
  'off',
  'often',
  'on',
  'only',
  'or',
  'other',
  'our',
  'own',
  'rather',
  'said',
  'say',
  'says',
  'she',
  'should',
  'since',
  'so',
  'some',
  'than',
  'that',
  'the',
  'their',
  'them',
  'then',
  'there',
  'these',
  'they',
  'this',
  'tis',
  'to',
  'too',
  'twas',
  'us',
  'wants',
  'was',
  'we',
  'were',
  'what',
  'when',
  'where',
  'which',
  'while',
  'who',
  'whom',
  'why',
  'will',
  'with',
  'would',
  'yet',
  'you',
  'your'
])

lunr.Pipeline.registerFunction(lunr.stopWordFilter, 'stopWordFilter')
/*!
 * lunr.trimmer
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * lunr.trimmer is a pipeline function for trimming non word
 * characters from the beginning and end of tokens before they
 * enter the index.
 *
 * This implementation may not work correctly for non latin
 * characters and should either be removed or adapted for use
 * with languages with non-latin characters.
 *
 * @static
 * @implements {lunr.PipelineFunction}
 * @param {lunr.Token} token The token to pass through the filter
 * @returns {lunr.Token}
 * @see lunr.Pipeline
 */
lunr.trimmer = function (token) {
  return token.update(function (s) {
    return s.replace(/^\W+/, '').replace(/\W+$/, '')
  })
}

lunr.Pipeline.registerFunction(lunr.trimmer, 'trimmer')
/*!
 * lunr.TokenSet
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * A token set is used to store the unique list of all tokens
 * within an index. Token sets are also used to represent an
 * incoming query to the index, this query token set and index
 * token set are then intersected to find which tokens to look
 * up in the inverted index.
 *
 * A token set can hold multiple tokens, as in the case of the
 * index token set, or it can hold a single token as in the
 * case of a simple query token set.
 *
 * Additionally token sets are used to perform wildcard matching.
 * Leading, contained and trailing wildcards are supported, and
 * from this edit distance matching can also be provided.
 *
 * Token sets are implemented as a minimal finite state automata,
 * where both common prefixes and suffixes are shared between tokens.
 * This helps to reduce the space used for storing the token set.
 *
 * @constructor
 */
lunr.TokenSet = function () {
  this.final = false
  this.edges = {}
  this.id = lunr.TokenSet._nextId
  lunr.TokenSet._nextId += 1
}

/**
 * Keeps track of the next, auto increment, identifier to assign
 * to a new tokenSet.
 *
 * TokenSets require a unique identifier to be correctly minimised.
 *
 * @private
 */
lunr.TokenSet._nextId = 1

/**
 * Creates a TokenSet instance from the given sorted array of words.
 *
 * @param {String[]} arr - A sorted array of strings to create the set from.
 * @returns {lunr.TokenSet}
 * @throws Will throw an error if the input array is not sorted.
 */
lunr.TokenSet.fromArray = function (arr) {
  var builder = new lunr.TokenSet.Builder

  for (var i = 0, len = arr.length; i < len; i++) {
    builder.insert(arr[i])
  }

  builder.finish()
  return builder.root
}

/**
 * Creates a token set from a query clause.
 *
 * @private
 * @param {Object} clause - A single clause from lunr.Query.
 * @param {string} clause.term - The query clause term.
 * @param {number} [clause.editDistance] - The optional edit distance for the term.
 * @returns {lunr.TokenSet}
 */
lunr.TokenSet.fromClause = function (clause) {
  if ('editDistance' in clause) {
    return lunr.TokenSet.fromFuzzyString(clause.term, clause.editDistance)
  } else {
    return lunr.TokenSet.fromString(clause.term)
  }
}

/**
 * Creates a token set representing a single string with a specified
 * edit distance.
 *
 * Insertions, deletions, substitutions and transpositions are each
 * treated as an edit distance of 1.
 *
 * Increasing the allowed edit distance will have a dramatic impact
 * on the performance of both creating and intersecting these TokenSets.
 * It is advised to keep the edit distance less than 3.
 *
 * @param {string} str - The string to create the token set from.
 * @param {number} editDistance - The allowed edit distance to match.
 * @returns {lunr.Vector}
 */
lunr.TokenSet.fromFuzzyString = function (str, editDistance) {
  var root = new lunr.TokenSet

  var stack = [{
    node: root,
    editsRemaining: editDistance,
    str: str
  }]

  while (stack.length) {
    var frame = stack.pop()

    // no edit
    if (frame.str.length > 0) {
      var char = frame.str.charAt(0),
          noEditNode

      if (char in frame.node.edges) {
        noEditNode = frame.node.edges[char]
      } else {
        noEditNode = new lunr.TokenSet
        frame.node.edges[char] = noEditNode
      }

      if (frame.str.length == 1) {
        noEditNode.final = true
      }

      stack.push({
        node: noEditNode,
        editsRemaining: frame.editsRemaining,
        str: frame.str.slice(1)
      })
    }

    if (frame.editsRemaining == 0) {
      continue
    }

    // insertion
    if ("*" in frame.node.edges) {
      var insertionNode = frame.node.edges["*"]
    } else {
      var insertionNode = new lunr.TokenSet
      frame.node.edges["*"] = insertionNode
    }

    if (frame.str.length == 0) {
      insertionNode.final = true
    }

    stack.push({
      node: insertionNode,
      editsRemaining: frame.editsRemaining - 1,
      str: frame.str
    })

    // deletion
    // can only do a deletion if we have enough edits remaining
    // and if there are characters left to delete in the string
    if (frame.str.length > 1) {
      stack.push({
        node: frame.node,
        editsRemaining: frame.editsRemaining - 1,
        str: frame.str.slice(1)
      })
    }

    // deletion
    // just removing the last character from the str
    if (frame.str.length == 1) {
      frame.node.final = true
    }

    // substitution
    // can only do a substitution if we have enough edits remaining
    // and if there are characters left to substitute
    if (frame.str.length >= 1) {
      if ("*" in frame.node.edges) {
        var substitutionNode = frame.node.edges["*"]
      } else {
        var substitutionNode = new lunr.TokenSet
        frame.node.edges["*"] = substitutionNode
      }

      if (frame.str.length == 1) {
        substitutionNode.final = true
      }

      stack.push({
        node: substitutionNode,
        editsRemaining: frame.editsRemaining - 1,
        str: frame.str.slice(1)
      })
    }

    // transposition
    // can only do a transposition if there are edits remaining
    // and there are enough characters to transpose
    if (frame.str.length > 1) {
      var charA = frame.str.charAt(0),
          charB = frame.str.charAt(1),
          transposeNode

      if (charB in frame.node.edges) {
        transposeNode = frame.node.edges[charB]
      } else {
        transposeNode = new lunr.TokenSet
        frame.node.edges[charB] = transposeNode
      }

      if (frame.str.length == 1) {
        transposeNode.final = true
      }

      stack.push({
        node: transposeNode,
        editsRemaining: frame.editsRemaining - 1,
        str: charA + frame.str.slice(2)
      })
    }
  }

  return root
}

/**
 * Creates a TokenSet from a string.
 *
 * The string may contain one or more wildcard characters (*)
 * that will allow wildcard matching when intersecting with
 * another TokenSet.
 *
 * @param {string} str - The string to create a TokenSet from.
 * @returns {lunr.TokenSet}
 */
lunr.TokenSet.fromString = function (str) {
  var node = new lunr.TokenSet,
      root = node

  /*
   * Iterates through all characters within the passed string
   * appending a node for each character.
   *
   * When a wildcard character is found then a self
   * referencing edge is introduced to continually match
   * any number of any characters.
   */
  for (var i = 0, len = str.length; i < len; i++) {
    var char = str[i],
        final = (i == len - 1)

    if (char == "*") {
      node.edges[char] = node
      node.final = final

    } else {
      var next = new lunr.TokenSet
      next.final = final

      node.edges[char] = next
      node = next
    }
  }

  return root
}

/**
 * Converts this TokenSet into an array of strings
 * contained within the TokenSet.
 *
 * This is not intended to be used on a TokenSet that
 * contains wildcards, in these cases the results are
 * undefined and are likely to cause an infinite loop.
 *
 * @returns {string[]}
 */
lunr.TokenSet.prototype.toArray = function () {
  var words = []

  var stack = [{
    prefix: "",
    node: this
  }]

  while (stack.length) {
    var frame = stack.pop(),
        edges = Object.keys(frame.node.edges),
        len = edges.length

    if (frame.node.final) {
      /* In Safari, at this point the prefix is sometimes corrupted, see:
       * https://github.com/olivernn/lunr.js/issues/279 Calling any
       * String.prototype method forces Safari to "cast" this string to what
       * it's supposed to be, fixing the bug. */
      frame.prefix.charAt(0)
      words.push(frame.prefix)
    }

    for (var i = 0; i < len; i++) {
      var edge = edges[i]

      stack.push({
        prefix: frame.prefix.concat(edge),
        node: frame.node.edges[edge]
      })
    }
  }

  return words
}

/**
 * Generates a string representation of a TokenSet.
 *
 * This is intended to allow TokenSets to be used as keys
 * in objects, largely to aid the construction and minimisation
 * of a TokenSet. As such it is not designed to be a human
 * friendly representation of the TokenSet.
 *
 * @returns {string}
 */
lunr.TokenSet.prototype.toString = function () {
  // NOTE: Using Object.keys here as this.edges is very likely
  // to enter 'hash-mode' with many keys being added
  //
  // avoiding a for-in loop here as it leads to the function
  // being de-optimised (at least in V8). From some simple
  // benchmarks the performance is comparable, but allowing
  // V8 to optimize may mean easy performance wins in the future.

  if (this._str) {
    return this._str
  }

  var str = this.final ? '1' : '0',
      labels = Object.keys(this.edges).sort(),
      len = labels.length

  for (var i = 0; i < len; i++) {
    var label = labels[i],
        node = this.edges[label]

    str = str + label + node.id
  }

  return str
}

/**
 * Returns a new TokenSet that is the intersection of
 * this TokenSet and the passed TokenSet.
 *
 * This intersection will take into account any wildcards
 * contained within the TokenSet.
 *
 * @param {lunr.TokenSet} b - An other TokenSet to intersect with.
 * @returns {lunr.TokenSet}
 */
lunr.TokenSet.prototype.intersect = function (b) {
  var output = new lunr.TokenSet,
      frame = undefined

  var stack = [{
    qNode: b,
    output: output,
    node: this
  }]

  while (stack.length) {
    frame = stack.pop()

    // NOTE: As with the #toString method, we are using
    // Object.keys and a for loop instead of a for-in loop
    // as both of these objects enter 'hash' mode, causing
    // the function to be de-optimised in V8
    var qEdges = Object.keys(frame.qNode.edges),
        qLen = qEdges.length,
        nEdges = Object.keys(frame.node.edges),
        nLen = nEdges.length

    for (var q = 0; q < qLen; q++) {
      var qEdge = qEdges[q]

      for (var n = 0; n < nLen; n++) {
        var nEdge = nEdges[n]

        if (nEdge == qEdge || qEdge == '*') {
          var node = frame.node.edges[nEdge],
              qNode = frame.qNode.edges[qEdge],
              final = node.final && qNode.final,
              next = undefined

          if (nEdge in frame.output.edges) {
            // an edge already exists for this character
            // no need to create a new node, just set the finality
            // bit unless this node is already final
            next = frame.output.edges[nEdge]
            next.final = next.final || final

          } else {
            // no edge exists yet, must create one
            // set the finality bit and insert it
            // into the output
            next = new lunr.TokenSet
            next.final = final
            frame.output.edges[nEdge] = next
          }

          stack.push({
            qNode: qNode,
            output: next,
            node: node
          })
        }
      }
    }
  }

  return output
}
lunr.TokenSet.Builder = function () {
  this.previousWord = ""
  this.root = new lunr.TokenSet
  this.uncheckedNodes = []
  this.minimizedNodes = {}
}

lunr.TokenSet.Builder.prototype.insert = function (word) {
  var node,
      commonPrefix = 0

  if (word < this.previousWord) {
    throw new Error ("Out of order word insertion")
  }

  for (var i = 0; i < word.length && i < this.previousWord.length; i++) {
    if (word[i] != this.previousWord[i]) break
    commonPrefix++
  }

  this.minimize(commonPrefix)

  if (this.uncheckedNodes.length == 0) {
    node = this.root
  } else {
    node = this.uncheckedNodes[this.uncheckedNodes.length - 1].child
  }

  for (var i = commonPrefix; i < word.length; i++) {
    var nextNode = new lunr.TokenSet,
        char = word[i]

    node.edges[char] = nextNode

    this.uncheckedNodes.push({
      parent: node,
      char: char,
      child: nextNode
    })

    node = nextNode
  }

  node.final = true
  this.previousWord = word
}

lunr.TokenSet.Builder.prototype.finish = function () {
  this.minimize(0)
}

lunr.TokenSet.Builder.prototype.minimize = function (downTo) {
  for (var i = this.uncheckedNodes.length - 1; i >= downTo; i--) {
    var node = this.uncheckedNodes[i],
        childKey = node.child.toString()

    if (childKey in this.minimizedNodes) {
      node.parent.edges[node.char] = this.minimizedNodes[childKey]
    } else {
      // Cache the key for this node since
      // we know it can't change anymore
      node.child._str = childKey

      this.minimizedNodes[childKey] = node.child
    }

    this.uncheckedNodes.pop()
  }
}
/*!
 * lunr.Index
 * Copyright (C) 2020 Oliver Nightingale
 */

/**
 * An index contains the built index of all documents and provides a query interface
 * to the index.
 *
 * Usually instances of lunr.Index will not be created using this constructor, instead
 * lunr.Builder should be used to construct new indexes, or lunr.Index.load should be
 * used to load previously built and serialized indexes.
 *
 * @constructor
 * @param {Object} attrs - The attributes of the built search index.
 * @param {Object} attrs.invertedIndex - An index of term/field to document reference.
 * @param {Object<string, lunr.Vector>} attrs.fieldVectors - Field vectors
 * @param {lunr.TokenSet} attrs.tokenSet - An set of all corpus tokens.
 * @param {string[]} attrs.fields - The names of indexed document fields.
 * @param {lunr.Pipeline} attrs.pipeline - The pipeline to use for search terms.
 */
lunr.Index = function (attrs) {
  this.invertedIndex = attrs.invertedIndex
  this.fieldVectors = attrs.fieldVectors
  this.tokenSet = attrs.tokenSet
  this.fields = attrs.fields
  this.pipeline = attrs.pipeline
}

/**
 * A result contains details of a document matching a search query.
 * @typedef {Object} lunr.Index~Result
 * @property {string} ref - The reference of the document this result represents.
 * @property {number} score - A number between 0 and 1 representing how similar this document is to the query.
 * @property {lunr.MatchData} matchData - Contains metadata about this match including which term(s) caused the match.
 */

/**
 * Although lunr provides the ability to create queries using lunr.Query, it also provides a simple
 * query language which itself is parsed into an instance of lunr.Query.
 *
 * For programmatically building queries it is advised to directly use lunr.Query, the query language
 * is best used for human entered text rather than program generated text.
 *
 * At its simplest queries can just be a single term, e.g. `hello`, multiple terms are also supported
 * and will be combined with OR, e.g `hello world` will match documents that contain either 'hello'
 * or 'world', though those that contain both will rank higher in the results.
 *
 * Wildcards can be included in terms to match one or more unspecified characters, these wildcards can
 * be inserted anywhere within the term, and more than one wildcard can exist in a single term. Adding
 * wildcards will increase the number of documents that will be found but can also have a negative
 * impact on query performance, especially with wildcards at the beginning of a term.
 *
 * Terms can be restricted to specific fields, e.g. `title:hello`, only documents with the term
 * hello in the title field will match this query. Using a field not present in the index will lead
 * to an error being thrown.
 *
 * Modifiers can also be added to terms, lunr supports edit distance and boost modifiers on terms. A term
 * boost will make documents matching that term score higher, e.g. `foo^5`. Edit distance is also supported
 * to provide fuzzy matching, e.g. 'hello~2' will match documents with hello with an edit distance of 2.
 * Avoid large values for edit distance to improve query performance.
 *
 * Each term also supports a presence modifier. By default a term's presence in document is optional, however
 * this can be changed to either required or prohibited. For a term's presence to be required in a document the
 * term should be prefixed with a '+', e.g. `+foo bar` is a search for documents that must contain 'foo' and
 * optionally contain 'bar'. Conversely a leading '-' sets the terms presence to prohibited, i.e. it must not
 * appear in a document, e.g. `-foo bar` is a search for documents that do not contain 'foo' but may contain 'bar'.
 *
 * To escape special characters the backslash character '\' can be used, this allows searches to include
 * characters that would normally be considered modifiers, e.g. `foo\~2` will search for a term "foo~2" instead
 * of attempting to apply a boost of 2 to the search term "foo".
 *
 * @typedef {string} lunr.Index~QueryString
 * @example <caption>Simple single term query</caption>
 * hello
 * @example <caption>Multiple term query</caption>
 * hello world
 * @example <caption>term scoped to a field</caption>
 * title:hello
 * @example <caption>term with a boost o