polyfill-service/polyfills/Object/setPrototypeOf/polyfill.js

A polyfill combinator

// ES6-shim 0.16.0 (c) 2013-2014 Paul Miller (http://paulmillr.com)
// ES6-shim may be freely distributed under the MIT license.
// For more details and documentation:
// https://github.com/paulmillr/es6-shim/

 // NOTE:  This versions needs object ownership
  //        because every promoted object needs to be reassigned
  //        otherwise uncompatible browsers cannot work as expected
  //
  // NOTE:  This might need es5-shim or polyfills upfront
  //        because it's based on ES5 API.
  //        (probably just an IE <= 8 problem)
  //
  // NOTE:  nodejs is fine in version 0.8, 0.10, and future versions.
(function () {
	if (Object.setPrototypeOf) { return; }

	/*jshint proto: true */
	// @author    Andrea Giammarchi - @WebReflection

	var getOwnPropertyNames = Object.getOwnPropertyNames;
	var getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor;
	var create = Object.create;
	var defineProperty = Object.defineProperty;
	var getPrototypeOf = Object.getPrototypeOf;
	var objProto = Object.prototype;

	var copyDescriptors = function (target, source) {
		// define into target descriptors from source
		getOwnPropertyNames(source).forEach(function (key) {
			defineProperty(
				target,
				key,
				getOwnPropertyDescriptor(source, key)
			);
		});
		return target;
	};
	// used as fallback when no promotion is possible
	var createAndCopy = function (origin, proto) {
		return copyDescriptors(create(proto), origin);
	};
	var set, setPrototypeOf;
	try {
		// this might fail for various reasons
		// ignore if Chrome cought it at runtime
		set = getOwnPropertyDescriptor(objProto, '__proto__').set;
		set.call({}, null);
		// setter not poisoned, it can promote
		// Firefox, Chrome
		setPrototypeOf = function (origin, proto) {
			set.call(origin, proto);
			return origin;
		};
	} catch (e) {
		// do one or more feature detections
		set = { __proto__: null };
		// if proto does not work, needs to fallback
		// some Opera, Rhino, ducktape
		if (set instanceof Object) {
			setPrototypeOf = createAndCopy;
		} else {
			// verify if null objects are buggy
			/* eslint-disable no-proto */
			set.__proto__ = objProto;
			/* eslint-enable no-proto */
			// if null objects are buggy
			// nodejs 0.8 to 0.10
			if (set instanceof Object) {
				setPrototypeOf = function (origin, proto) {
					// use such bug to promote
					/* eslint-disable no-proto */
					origin.__proto__ = proto;
					/* eslint-enable no-proto */
					return origin;
				};
			} else {
				// try to use proto or fallback
				// Safari, old Firefox, many others
				setPrototypeOf = function (origin, proto) {
					// if proto is not null
					if (getPrototypeOf(origin)) {
						// use __proto__ to promote
						/* eslint-disable no-proto */
						origin.__proto__ = proto;
						/* eslint-enable no-proto */
						return origin;
					} else {
						// otherwise unable to promote: fallback
						return createAndCopy(origin, proto);
					}
				};
			}
		}
	}
	Object.setPrototypeOf = setPrototypeOf;
}());