property-reflection.js

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/* Any copyright is dedicated to the Public Domain.

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

// Basic tests for standard Object APIs interacting with symbols.

// Object.defineProperty

function F() {}

var f = new F;

Object.defineProperty(f, Symbol.for("name"), {

    configurable: true,

    value: "eff"

});

assertEq("name" in f, false);

assertEq("Symbol(name)" in f, false);

assertEq(Symbol.for("name") in f, true);

assertEq(f[Symbol.for("name")], "eff");

// Object.defineProperties

function D() {}

var descs = new D;

var s1 = Symbol("s1");

var hits = 0;

descs[s1] = {

    get: () => hits++,

    set: undefined,

    enumerable: true,

    configurable: true

};

var s2 = Symbol("s2");

descs[s2] = {

    value: {},

    writable: true,

    enumerable: false,

    configurable: true

};

var s3 = Symbol("s3");

D.prototype[s3] = {value: "FAIL"};

assertEq(Object.defineProperties(f, descs), f);

assertEq(s1 in f, true);

assertEq(f[s1], 0);

assertEq(hits, 1);

assertEq(s2 in f, true);

assertEq(f[s2], descs[s2].value);

assertEq(s3 in f, false);

// Object.create

var n = Object.create({}, descs);

assertEq(s1 in n, true);

assertEq(n[s1], 1);

assertEq(hits, 2);

assertEq(s2 in n, true);

assertEq(n[s2], descs[s2].value);

assertEq(s3 in n, false);

// Object.getOwnPropertyDescriptor

var desc = Object.getOwnPropertyDescriptor(n, s1);

assertDeepEq(desc, descs[s1]);

assertEq(desc.get, descs[s1].get);

desc = Object.getOwnPropertyDescriptor(n, s2);

assertDeepEq(desc, descs[s2]);

assertEq(desc.value, descs[s2].value);

// Object.prototype.hasOwnProperty

assertEq(descs.hasOwnProperty(s1), true);

assertEq(descs.hasOwnProperty(s2), true);

assertEq(descs.hasOwnProperty(s3), false);

assertEq([].hasOwnProperty(Symbol.iterator), false);

assertEq(Array.prototype.hasOwnProperty(Symbol.iterator), true);

// Object.prototype.propertyIsEnumerable

assertEq(n.propertyIsEnumerable(s1), true);

assertEq(n.propertyIsEnumerable(s2), false);

assertEq(n.propertyIsEnumerable(s3), false);  // no such property

assertEq(D.prototype.propertyIsEnumerable(s3), true);

assertEq(descs.propertyIsEnumerable(s3), false); // inherited properties are not considered

// Object.preventExtensions

var obj = {};

obj[s1] = 1;

assertEq(Object.preventExtensions(obj), obj);

assertThrowsInstanceOf(function () { "use strict"; obj[s2] = 2; }, TypeError);

obj[s2] = 2;  // still no effect

assertEq(s2 in obj, false);

// Object.isSealed, Object.isFrozen

assertEq(Object.isSealed(obj), false);

assertEq(Object.isFrozen(obj), false);

assertEq(delete obj[s1], true);

assertEq(Object.isSealed(obj), true);

assertEq(Object.isFrozen(obj), true);

obj = {};

obj[s1] = 1;

Object.preventExtensions(obj);

Object.defineProperty(obj, s1, {configurable: false});  // still writable

assertEq(Object.isSealed(obj), true);

assertEq(Object.isFrozen(obj), false);

obj[s1] = 2;

assertEq(obj[s1], 2);

Object.defineProperty(obj, s1, {writable: false});

assertEq(Object.isFrozen(obj), true);

// Object.seal, Object.freeze

var obj = {};

obj[s1] = 1;

Object.seal(obj);

desc = Object.getOwnPropertyDescriptor(obj, s1);

assertEq(desc.configurable, false);

assertEq(desc.writable, true);

Object.freeze(obj);

assertEq(Object.getOwnPropertyDescriptor(obj, s1).writable, false);

// Object.setPrototypeOf purges caches for symbol-keyed properties.

var proto = {};

proto[s1] = 1;

Object.defineProperty(proto, s2, {

    get: () => 2,

    set: v => undefined

});

var obj = Object.create(proto);

var last1, last2;

var N = 9;

for (var i = 0; i < N; i++) {

    last1 = obj[s1];

    last2 = obj[s2];

    obj[s2] = "marker";

    if (i === N - 2)

        Object.setPrototypeOf(obj, {});

assertEq(last1, undefined);

assertEq(last2, undefined);

assertEq(obj.hasOwnProperty(s2), true);

assertEq(obj[s2], "marker");

if (typeof reportCompare === "function")

    reportCompare(0, 0);