es6-weakmap.js: ECMA-262 6th Edition (ECMAScript 2015) WeakMap polyfill

es6-weakmap.js

/**
 * es6-weakmap.js
 * WeakMap (ECMA-262 6th Edition / ECMAScript 2015)
 *
 *
 * @version 0.9.2
 * @author think49
 * @url https://gist.github.com/think49/283b7374e352e09fc131
 * @license http://www.opensource.org/licenses/mit-license.php (The MIT License)
 * @see <a href="http://www.ecma-international.org/ecma-262/6.0/#sec-weakmap-constructor">23.3.1 The WeakMap Constructor – ECMA-262 6th Edition</a>
 */
'use strict';
if (typeof WeakMap !== 'function' && typeof Object.defineProperties === 'function') {
  var WeakMap = (function (Object, isArray) {
    var weakMapDataList = []; // [[WeakMapData]] internal slot

    function WeakMap (/* [iterable] */) {
      weakMapDataList.push([this, []]);
    }

    Object.defineProperties(WeakMap.prototype, {
      get: {
        writable: true,
        enumerable: false,
        configurable: true,
        value: function get (key) {
          if (Object(this) !== this) { // 2. If Type(thisArg) is not Object, throw a TypeError exception.
            throw new TypeError('Method WeakMap.prototype.get called on incompatible receiver ' + this);
          }

          var i = 0,
              l = weakMapDataList.length,
              weakMapData, map, data;

          while (i < l) {
            weakMapData = weakMapDataList[i++];

            if (weakMapData[0] === this) {
              if (Object(key) !== key) {  // 5. If Type(key) is not Object, return undefined.
                return;
              }

              map = weakMapData[1];
              i = 0,
              l = map.length;
              while (i < l) {
                data = map[i++];
                if (data[0] === key) {
                  return data[1];
                }
              }
              return;
            }
          }

          throw new TypeError('Method WeakMap.prototype.get called on incompatible receiver ' + this);  // 3. If thisArg does not have a [[WeakMapData]] internal slot, throw a TypeError exception.
        }
      },
      set: {
        writable: true,
        enumerable: false,
        configurable: true,
        value: function set (key, value) {
          if (Object(this) !== this) {  // 2. If Type(thisArg) is not Object, throw a TypeError exception.
            throw new TypeError('Method WeakMap.prototype.set called on incompatible receiver ' + this);
          }

          var i = 0,
              l = weakMapDataList.length,
              weakMapData, map, data;

          while (i < l) {
            weakMapData = weakMapDataList[i++];

            if (weakMapData[0] === this) {
              if (Object(key) !== key) {  // 5. If Type(key) is not Object, throw a TypeError exception.
                throw new TypeError('Invalid value used as weak map key');
              }

              map = weakMapData[1];
              i = 0,
              l = map.length;
              while (i < l) {
                data = map[i++];
                if (data[0] === key) {
                  data[1] = value;
                  return this;
                }
              }

              map.push([key, value]);
              return this;
            }
          }

          throw new TypeError('Method WeakMap.prototype.set called on incompatible receiver ' + this);  // 3. If thisArg does not have a [[WeakMapData]] internal slot, throw a TypeError exception.
        }
      },
      has: {
        writable: true,
        enumerable: false,
        configurable: true,
        value: function has (key) {
          if (Object(this) !== this) {  // 2. If Type(thisArg) is not Object, throw a TypeError exception.exception.
            throw new TypeError('Method WeakMap.prototype.has called on incompatible receiver ' + this);
          }

          var i = 0,
              l = weakMapDataList.length,
              weakMapData, map;

          while (i < l) {
            weakMapData = weakMapDataList[i++]; // [[WeakMapData]] internal slot

            if (weakMapData[0] === this) {
              if (Object(key) !== key) {  // 5. If Type(key) is not Object, return false.
                return false;
              }

              map = weakMapData[1];
              i = 0,
              l = map.length;
              while (i < l) {
                if (map[i++][0] === key) {
                  return true;
                }
              }

              return false;
            }
          }

          throw new TypeError('Method WeakMap.prototype.has called on incompatible receiver ' + this);  // 3. If thisArg does not have a [[WeakMapData]] internal slot, throw a TypeError exception.
        }
      },
      delete: {
        writable: true,
        enumerable: false,
        configurable: true,
        value: function delete_ (key) { // Note: If you specify the "delete" for SyntaxError occurs, it is replaced by "delete_"
          if (Object(this) !== this) {  // 2. If Type(thisArg) is not Object, throw a TypeError exception.
            throw new TypeError('Method WeakMap.prototype.delete called on incompatible receiver ' + this);
          }

          var i = 0,
              l = weakMapDataList.length,
              weakMapData, map;

          while (i < l) {
            weakMapData = weakMapDataList[i++]; // [[WeakMapData]] internal slot

            if (weakMapData[0] === this) {
              if (Object(key) !== key) {  // 5. If Type(key) is not Object, return false.
                return false;
              }

              map = weakMapData[1];
              i = 0,
              l = map.length;
              while (i < l) {
                if (map[i++][0] === key) {
                  weakMapData[1] = map.slice(0, i - 1).concat(map.slice(i));
                  return true;
                }
              }

              return false;
            }
          }

          throw new TypeError('Method WeakMap.prototype.delete called on incompatible receiver ' + this);  // 3. If thisArg does not have a [[WeakMapData]] internal slot, throw a TypeError exception.
        }
      }
    });

    return WeakMap;
  }(Object, Array.isArray));
}

ECMA-262 6th Edition

• 23.3.1.1 WeakMap([iterable]) – ECMA-262 6th Edition
• 23.3.3.2 WeakMap.prototype.delete(key) – ECMA-262 6th Edition
• 23.3.3.3 WeakMap.prototype.get(key) – ECMA-262 6th Edition
• 23.3.3.4 WeakMap.prototype.has(key) – ECMA-262 6th Edition
• 23.3.3.5 WeakMap.prototype.set(key, value) – ECMA-262 6th Edition