@dbl0null/slow-json-stringify/dist/sjs.js

The slow.. well actually fastest JSON stringifier in the galaxy.

const _replaceString = type => type.indexOf('string') !== -1 ? '"__par__"' : '__par__'; // 3 possibilities after arbitrary property:
// - ", => non-last string property
// - , => non-last non-string property
// - " => last string property


const _matchStartRe = /^(",|,|")/;
const _chunkRegex = /"\w+__sjs"/g;
/**
 * @param {string} str - prepared string already validated.
 * @param {array} queue - queue containing the property name to match
 * (used for building dynamic regex) needed for the preparation of
 * chunks used in different scenarios.
 */

const _makeChunks = (str, queue) => {
  const chunks = str // Matching prepared properties and replacing with target with or without
  // double quotes.
  // => Avoiding unnecessary concatenation of doublequotes during serialization.
  .replace(_chunkRegex, _replaceString).split('__par__');
  const result = [];

  let _i;

  const length = chunks.length;

  for (let i = 0; i < length; ++i) {
    var _queue$i;

    const chunk = chunks[i]; // Using dynamic regex to ensure that only the correct property
    // at the end of the string it's actually selected.
    // => e.g. ,"a":{"a": => ,"a":{

    const matchProp = `("${(_queue$i = queue[i]) == null ? void 0 : _queue$i.name}":("?))$`; // Check if current chunk is the last one inside a nested property

    const isLast = (_i = i + 1) === length || (_i = chunks[_i].indexOf('}')) && (_i === 0 || _i === 1); // If the chunk is the last one the `isUndef` case should match
    // the preceding comma too.


    const matchPropRe = new RegExp(isLast ? `(,?)${matchProp}` : matchProp);
    const withoutInitial = chunk.replace(_matchStartRe, '');
    result.push({
      // notify that the chunk preceding the current one has not
      // its corresponding property undefined.
      // => This is a V8 optimization as it's way faster writing
      // the value of a property than writing the entire property.
      flag: false,
      pure: chunk,
      // Without initial part
      prevUndef: withoutInitial,
      // Without property chars
      isUndef: chunk.replace(matchPropRe, ''),
      // Only remaining chars (can be zero chars)
      bothUndef: withoutInitial.replace(matchPropRe, '')
    });
  }

  return result;
};

/**
 * `_find` is a super fast deep property finder.
 * It dynamically build the function needed to reach the desired
 * property.
 *
 * e.g.
 * obj = {a: {b: {c: 1}}}
 * _find(['a','b','c']) => (obj) => (((obj || {}).a || {}).b || {}).c
 *
 * @param {array} path - path to reach object property.
 */

const __find = path => {
  let str = 'obj';

  for (let i = 0; i < path.length; ++i) {
    str += `?.['${path[i]}']`;
  }

  return eval(`(obj => ${str})`);
};

function _arraySerializer(serializer, array) {
  // Stringifying more complex array using the provided sjs schema
  let acc = '';
  const len = array.length - 1;

  for (let i = 0; i < len; ++i) {
    acc += `${serializer(array[i])},`;
  } // Prevent slice for removing unnecessary comma.


  acc += serializer(array[len]);
  return `[${acc}]`;
}
/**
 * `_makeArraySerializer` is simply a wrapper of another `sjs` schema
 * used for the serialization of arrais.
 */


const _makeArraySerializer = serializer => {
  if (typeof serializer === 'function') return _arraySerializer.bind(undefined, serializer);
  return JSON.stringify;
};

const fnUser = value => value;
/**
 * @param type number|string|boolean|array|null
 * @param serializer
 * @returns
 */


const attr = (type, serializer) => {
  const usedSerializer = serializer || fnUser;
  return {
    isSJS: true,
    type,
    serializer: type === 'array' ? _makeArraySerializer(serializer) : usedSerializer
  };
}; // Little utility for escaping convenience.
// => if no regex is provided, a default one will be used.


const _defaultRegex = /[\t\n\r"\\]/g;

const _escapeCallback = char => '\\' + char;

const escape = (regex = _defaultRegex) => str => str.replace(regex, _escapeCallback);

/**
 * @param {object} originalSchema
 * @param {array} queue
 * @param {string|object} obj
 * @param {array} acc
 */

function _prepareQueue(originalSchema, queue, obj, acc = []) {
  // this looks weird for objects, but is actually exactly what we want: object.toString() === '[object Object]'. We only want actual strings.
  if (obj.toString().indexOf('__sjs') !== -1) {
    const find = __find(acc);

    const {
      serializer
    } = find(originalSchema);
    queue.push({
      serializer,
      find,
      name: acc[acc.length - 1]
    });
    return;
  } // Recursively going deeper.
  // NOTE: While going deeper, the current prop is pushed into the accumulator
  // to keep track of the position inside of the object.


  const keys = Object.keys(obj);

  for (let i = 0; i < keys.length; ++i) {
    const key = keys[i];

    _prepareQueue(originalSchema, queue, obj[key], [...acc, key]);
  }
}
/**
 * @param {object} preparedSchema - schema already validated
 * with modified prop values to avoid clashes.
 * @param {object} originalSchema - User provided schema
 * => contains array stringification serializers that are lost during preparation.
 */


const _makeQueue = (preparedSchema, originalSchema) => {
  const queue = [];

  _prepareQueue(originalSchema, queue, preparedSchema);

  return queue;
};

const _stringifyCallback = (_, value) => {
  if (!value.isSJS) return value;
  return `${value.type}__sjs`;
};
/**
 * `_prepare` - aims to normalize the schema provided by the user.
 * It will convert the schema in both a parseable string and an object
 * useable for making the chunks needed for the serialization part.
 * @param {object} schema - user provided schema
 */


const _prepare = schema => {
  const _preparedString = JSON.stringify(schema, _stringifyCallback);

  const _preparedSchema = JSON.parse(_preparedString);

  return {
    _preparedString,
    _preparedSchema
  };
};

/**
 * `select` function takes all the possible chunks from the
 * current index and set the more appropriate one in relation
 * to the current `value` and the `flag` state.
 *
 * => This approach avoids the use of Regex during serialization.
 *
 * @param {any} chunks - value to serialize.
 */
const _select = chunks => (value, index) => {
  const chunk = chunks[index];

  if (value !== undefined) {
    if (chunk.flag) {
      return chunk.prevUndef + value;
    }

    return chunk.pure + value;
  } // If the current value is undefined set a flag on the next
  // chunk stating that the previous prop is undefined.


  chunks[index + 1].flag = true;

  if (chunk.flag) {
    return chunk.bothUndef;
  }

  return chunk.isUndef;
};

// the stringification.

const sjs = schema => {
  const {
    _preparedString,
    _preparedSchema
  } = _prepare(schema); // Providing preparedSchema for univocal correspondence between created queue and chunks.
  // Provided original schema to keep track of the original properties that gets destroied
  // during schema preparation => e.g. array stringification method.


  const queue = _makeQueue(_preparedSchema, schema);

  const chunks = _makeChunks(_preparedString, queue);

  const selectChunk = _select(chunks); // Exposed function


  return obj => {
    let temp = '';

    for (let i = 0; i < queue.length; ++i) {
      const {
        serializer,
        find
      } = queue[i];
      const raw = find(obj);
      temp += selectChunk(serializer(raw), i);
    }

    const {
      flag,
      pure,
      prevUndef
    } = chunks[chunks.length - 1];
    return temp + (flag ? prevUndef : pure);
  };
};

exports.attr = attr;
exports.escape = escape;
exports.sjs = sjs;
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