setPrototypeOf.js - mozsearch

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/* Any copyright is dedicated to the Public Domain.

 * http://creativecommons.org/licenses/publicdomain/ */

// Reflect.setPrototypeOf changes an object's [[Prototype]].

var obj = {};

assertEq(Object.getPrototypeOf(obj), Object.prototype);

var proto = {};

assertEq(Reflect.setPrototypeOf(obj, proto), true);

assertEq(Object.getPrototypeOf(obj), proto);

// It can change an object's [[Prototype]] to null.

obj = {};

assertEq(Reflect.setPrototypeOf(obj, null), true);

assertEq(Object.getPrototypeOf(obj), null);

// The proto argument is required too.

obj = {};

assertThrowsInstanceOf(() => Reflect.setPrototypeOf(obj), TypeError);

// The proto argument must be either null or an object.

for (proto of [undefined, false, 0, 1.6, "that", Symbol.iterator]) {

    assertThrowsInstanceOf(() => Reflect.setPrototypeOf(obj, proto), TypeError);

// Return false if the target isn't extensible.

proto = {};

obj = Object.preventExtensions(Object.create(proto));

assertEq(Reflect.setPrototypeOf(obj, {}), false);

assertEq(Reflect.setPrototypeOf(obj, null), false);

assertEq(Reflect.setPrototypeOf(obj, proto), true);  // except if not changing anything

// Return false rather than create a [[Prototype]] cycle.

obj = {};

assertEq(Reflect.setPrototypeOf(obj, obj), false);

// Don't create a [[Prototype]] cycle involving 2 objects.

obj = Object.create(proto);

assertEq(Reflect.setPrototypeOf(proto, obj), false);

// Don't create a longish [[Prototype]] cycle.

for (var i = 0; i < 256; i++)

    obj = Object.create(obj);

assertEq(Reflect.setPrototypeOf(proto, obj), false);

// The spec claims we should allow creating cycles involving proxies. (The

// cycle check quietly exits on encountering the proxy.)

obj = {};

var proxy = new Proxy(Object.create(obj), {});

assertEq(Reflect.setPrototypeOf(obj, proxy), true);

assertEq(Reflect.getPrototypeOf(obj), proxy);

assertEq(Reflect.getPrototypeOf(proxy), obj);

// If a proxy handler returns a false-y value, return false.

var hits = 0;

proto = {name: "proto"};

obj = {name: "obj"};

proxy = new Proxy(obj, {

    setPrototypeOf(t, p) {

        assertEq(t, obj);

        assertEq(p, proto);

        hits++;

        return 0;

});

assertEq(Reflect.setPrototypeOf(proxy, proto), false);

assertEq(hits, 1);

// For more Reflect.setPrototypeOf tests, see target.js.

reportCompare(0, 0);