patella/dist/patella.cjs.js

Patella is a library for reactive programming in JavaScript, inspired by Hyperactiv and Vue.js.

// Global object/function references
var _Object = Object;
var _Object_hasOwnProperty = _Object.hasOwnProperty;
var _Array_isArray = Array.isArray;
var _Error = Error;
var _TypeError = TypeError;

/** Reference to global Object.defineProperty */
var defineProperty = _Object.defineProperty;

/**
 * Checks if an object has a specified property as its own property (ignores prototype properties and `__proto__`)
 * @param object Object to check
 * @param key Property key
 * @returns Does `object` have the property `key`?
 */
function hasOwnProperty(object, key) {
  return key !== "__proto__" && _Object_hasOwnProperty.call(object, key);
}

/**
 * Creates an ECMAScript 6 Symbol, falling back to a simple string in environments that do not support Symbols
 * @param description Symbol description
 * @returns Symbol object or string
 * @function
 */
/* c8 ignore start */
/* istanbul ignore next */
var createSymbol =
  typeof Symbol === "function"
    ? Symbol
    : function (description) {
        return "__" + description;
      };
/* c8 ignore stop */

/** Hint property to indicate if an object has been observed */
var HINT_OBSERVE = createSymbol("observe");
/** Hint property to indicate if a function has been disposed */
var HINT_DISPOSE = createSymbol("dispose");
/** Hint property that contains a function's dependency disposal callbacks */
var HINT_DEPENDS = createSymbol("depends");

/**
 * Defines a hint property on an object
 * @param object Object to define property on
 * @param hint Property key
 * @param {*} [value] Property value, property will be made non-configurable if this is unset (`undefined`)
 */
function defineHint(object, hint, value) {
  defineProperty(object, hint, {
    value: value,
    configurable: value !== void 0,
    enumerable: false,
    writable: false
  });
}

/**
 * Checks if a value is a normal object, ignores functions and arrays
 * @param value Value to check
 * @returns Is `value` a normal object?
 */
function isObject(value) {
  return value !== null && typeof value === "object" && !_Array_isArray(value);
}

/**
 * Checks if a value is a function
 * @param value Value to check
 * @return Is `value` a function?
 */
function isFunction(value) {
  return typeof value === "function";
}

/** Error message printed when an argument is of an incorrect type (not a normal object) */
var MESSAGE_NOT_OBJECT = "Argument 'object' is not an object";
/** Error message printed when an argument is of an incorrect type (not a function) */
var MESSAGE_NOT_FUNCTION = "Argument 'func' is not a function";

/**
 * Throws an error message
 * @param message Message to construct the error with
 * @param generic Should the more generic `Error` be thrown instead of `TypeError`?
 */
function throwError(message, generic) {
  throw new (generic ? _Error : _TypeError)(message);
}

/** Maximum queue length */
var MAX_QUEUE = 2000;

/** Is the queue being executed? */
var computedLock = false;
/** Queue of computed functions to be called */
var computedQueue = [];
/** Current index into `computedQueue` */
var computedI = 0;

/**
 * Throws an error indicating that the computed queue has overflowed
 */
function computedOverflow() {
  var message = "Computed queue overflow! Last 10 functions in the queue:";

  var length = computedQueue.length;
  for (var i = length - 11; i < length; i++) {
    var func = computedQueue[i];
    message +=
      "\n"
      + (i + 1)
      + ": "
      + (func.name || "anonymous");
  }

  throwError(message, true);
}

/**
 * Attempts to add a function to the computed queue, then attempts to lock and execute the computed queue
 * @param func Function to queue
 */
function computedNotify(func) {
  if (hasOwnProperty(func, HINT_DISPOSE)) return;

  // Only add to the queue if not already pending execution
  if (computedQueue.lastIndexOf(func) >= computedI) return;
  computedQueue.push(func);

  // Make sure that the function in question has a depends hint
  if (!hasOwnProperty(func, HINT_DEPENDS)) {
    defineHint(func, HINT_DEPENDS, []);
  }

  // Attempt to lock and execute the queue
  if (!computedLock) {
    computedLock = true;

    try {
      for (; computedI < computedQueue.length; computedI++) {
        // Indirectly call the function to avoid leaking `computedQueue` as `this`
        (0, computedQueue[computedI])();
        if (computedI > MAX_QUEUE) /* @__NOINLINE */ computedOverflow();
      }
    } finally {
      computedLock = false;
      computedQueue = [];
      computedI = 0;
    }
  }
}

/** See lib/patella.d.ts */
function computed(func) {
  if (!isFunction(func)) {
    throwError(MESSAGE_NOT_FUNCTION);
  }

  computedNotify(func);
  return func;
}

/**
 * Generates a property descriptor for a reactive property
 * @param value Initial property value
 * @returns Property descriptor object
 */
function reactiveProperty(value) {
  if (isObject(value)) reactiveObserve(value);

  // List of computed functions that depend on this property
  var depends = [];
  /**
   * Remove a computed function from this reactive property
   * @param func Computed function to remove
   */
  function dependsRemove(func) {
    var i = depends.lastIndexOf(func);
    if (i >= 0) depends.splice(i, 1);
  }

  return {
    get: function() {
      // Add the current executing computed function to this reactive property's dependencies
      var func = computedQueue[computedI];
      if (func) {
        var i = depends.lastIndexOf(func);
        if (i < 0) {
          // Add them to our dependencies
          depends.push(func);
          // Add us to their dependants
          func[HINT_DEPENDS].push(dependsRemove);
        }
      }

      return value;
    },
    set: function(newValue) {
      if (isObject(newValue)) reactiveObserve(newValue);
      value = newValue;

      // Notify all dependencies
      for (var i = 0; i < depends.length; i++) {
        computedNotify(depends[i]);
      }
    }
  };
}

/**
 * Observes an object by making all of its enumerable properties reactive
 * @param object Object to observe
 */
function reactiveObserve(object) {
  if (hasOwnProperty(object, HINT_OBSERVE)) return;
  defineHint(object, HINT_OBSERVE);

  for (var key in object) {
    if (hasOwnProperty(object, key)) {
      try {
        defineProperty(object, key, reactiveProperty(object[key]));
      } catch (err) {}
    }
  }
}

/** See lib/patella.d.ts */
function observe(object) {
  if (!isObject(object) && !isFunction(object)) {
    throwError(MESSAGE_NOT_OBJECT);
  }

  reactiveObserve(object);
  return object;
}

/** See lib/patella.d.ts */
function ignore(object) {
  if (!isObject(object) && !isFunction(object)) {
    throwError(MESSAGE_NOT_OBJECT);
  }

  if (!hasOwnProperty(object, HINT_OBSERVE)) {
    defineHint(object, HINT_OBSERVE);
  }

  return object;
}

/** See lib/patella.d.ts */
function dispose(func, clean) {
  if (func == null) {
    func = computedQueue[computedI];
    if (!func) {
      throwError("Tried to dispose of current computed function while not running a computed function", true);
    }
  } else if (!isFunction(func)) {
    throwError(MESSAGE_NOT_FUNCTION);
  }

  // Only execute if the function has not been disposed yet
  if (!hasOwnProperty(func, HINT_DISPOSE)) {
    // Only define disposed property if we aren't cleaning
    if (!clean) defineHint(func, HINT_DISPOSE);

    // Remove from dependant reactive objects
    var depends = func[HINT_DEPENDS];
    if (depends) {
      defineHint(func, HINT_DEPENDS, clean ? [] : void 0);
      for (var i = 0; i < depends.length; i++) {
        depends[i](func);
      }
    }

    // Remove from the queue if locked and pending execution
    if (computedLock) { // Not required, but saves a `lastIndexOf` call on an empty array for like 6 bytes
      var i = computedQueue.lastIndexOf(func);
      if (i > computedI) computedQueue.splice(i, 1);
    }
  }

  // Only return the function if it was specified as an argument
  if (!computedLock) return func;
}

exports.computed = computed;
exports.dispose = dispose;
exports.ignore = ignore;
exports.observe = observe;
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