ima/polyfill/collectionEnumeration.js

// @client-side

// fix for-of for Maps and Sets in IE9 & IE10
if (!Map.prototype[Symbol.iterator]) {
  Map.prototype[Symbol.iterator] = function() {
    return this.entries();
  };
}
if (!Set.prototype[Symbol.iterator]) {
  Set.prototype[Symbol.iterator] = function() {
    return this.values();
  };
}

[Map, Set].forEach(function(collection) {
  if (!new collection().entries()[Symbol.iterator]) {
    var entriesMethod = collection.prototype.entries;
    collection.prototype.entries = function() {
      var iterator = entriesMethod.call(this);
      iterator[Symbol.iterator] = function() {
        return iterator;
      };
      return iterator;
    };
  }
  if (!new collection().keys()[Symbol.iterator]) {
    var keysMethod = collection.prototype.keys;
    collection.prototype.keys = function() {
      var iterator = keysMethod.call(this);
      iterator[Symbol.iterator] = function() {
        return iterator;
      };
      return iterator;
    };
  }
  if (!new collection().values()[Symbol.iterator]) {
    var valuesMethod = collection.prototype.values;
    collection.prototype.values = function() {
      var iterator = valuesMethod.call(this);
      iterator[Symbol.iterator] = function() {
        return iterator;
      };
      return iterator;
    };
  }
});