runtime/shared/polyfill/objectSetPrototypeOf.js

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

/* eslint-disable */

// https://gist.github.com/WebReflection/5593554

/* istanbul ignore if */
if (!Object.setPrototypeOf) {
  Object.setPrototypeOf = (function(Object, magic) {
    var set;
    function setPrototypeOf(O, proto) {
      set.call(O, proto);
      return O;
    }
    try {
      // this works already in Firefox and Safari
      set = Object.getOwnPropertyDescriptor(Object.prototype, magic).set;
      set.call({}, null);
    } catch (e) {
      if (
        // IE < 11 cannot be shimmed
        Object.prototype !== {}[magic] ||
        // neither can any browser that actually
        // implemented __proto__ correctly
        // (all but old V8 will return here)
        {__proto__: null}.__proto__ === void 0
        // this case means null objects cannot be passed
        // through setPrototypeOf in a reliable way
        // which means here a **Sham** is needed instead
      ) {
        return;
      }
      // nodejs 0.8 and 0.10 are (buggy and..) fine here
      // probably Chrome or some old Mobile stock browser
      set = function(proto) {
        this[magic] = proto;
      };
      // please note that this will **not** work
      // in those browsers that do not inherit
      // __proto__ by mistake from Object.prototype
      // in these cases we should probably throw an error
      // or at least be informed about the issue
      setPrototypeOf.polyfill = setPrototypeOf(
        setPrototypeOf({}, null),
        Object.prototype
      ) instanceof Object;
      // setPrototypeOf.polyfill === true means it works as meant
      // setPrototypeOf.polyfill === false means it's not 100% reliable
      // setPrototypeOf.polyfill === undefined
      // or
      // setPrototypeOf.polyfill ==  null means it's not a polyfill
      // which means it works as expected
      // we can even delete Object.prototype.__proto__;
    }
    return setPrototypeOf;
  }(Object, '__proto__'));
}