com.google.javascript.jscomp.js.es6.util.construct.js Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of closure-compiler Show documentation

Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

There is a newer version: v20240317

Show newest version

/*
 * Copyright 2016 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @fileoverview
 * @suppress {uselessCode}
 */

'require util/objectcreate';
'require util/polyfill';
'require util/shouldpolyfill';

/**
 * Find or create a method that implements the behavior of `Reflect.construct`.
 *
 * @return {!Function}
 */
$jscomp.getConstructImplementation = function() {
  // Check for https://github.com/Microsoft/ChakraCore/issues/3217
  /** @return {boolean} */
  function reflectConstructWorks() {
    /** @constructor */ function Base() {}
    /** @constructor */ function Derived() {}
    new Base();
    Reflect.construct(Base, [], Derived);
    return new Base() instanceof Base;
  }

  if ($jscomp.TRUST_ES6_POLYFILLS && typeof Reflect != 'undefined' &&
      Reflect.construct) {
    if (reflectConstructWorks()) return Reflect.construct;
    var brokenConstruct = Reflect.construct;
    /**
     * @param {function(new: ?, ...?)} target The constructor to call.
     * @param {!Array} argList The arguments as a list.
     * @param {function(new: TARGET, ...?)=} opt_newTarget The constructor to
     *     instantiate.
     * @return {TARGET} The result of the function call.
     * @template TARGET
     * @suppress {reportUnknownTypes}
     */
    var patchedConstruct = function(target, argList, opt_newTarget) {
      var out = brokenConstruct(target, argList);
      if (opt_newTarget) Reflect.setPrototypeOf(out, opt_newTarget.prototype);
      return out;
    };
    return patchedConstruct;
  }

  /**
   * @param {function(new: ?, ...?)} target The constructor to call.
   * @param {!Array} argList The arguments as a list.
   * @param {function(new: TARGET, ...?)=} opt_newTarget The constructor to
   *     instantiate.
   * @return {TARGET} The result of the function call.
   * @template TARGET
   * @suppress {reportUnknownTypes}
   */
  function construct(target, argList, opt_newTarget) {
    if (opt_newTarget === undefined) opt_newTarget = target;
    var proto = opt_newTarget.prototype || Object.prototype;
    var obj = $jscomp.objectCreate(proto);
    var apply = Function.prototype.apply;
    var out = apply.call(target, obj, argList);
    return out || obj;
  }
  return construct;
};

/**
 * Polyfill for Reflect.construct() method:
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/construct
 *
 * The call to `$jscomp.getConstructImplementation()` is wrapped up as an object
 * literal `valueOf()` call in order to hide the (meaningless) side-effects
 * it contains that would otherwise prevent its definition from being removed,
 * even when nothing refers to `$jscomp.construct`.
 * @const
 */
$jscomp.construct =
    /** @type {typeof Reflect.construct} */ (
        {valueOf: $jscomp.getConstructImplementation}.valueOf());