getOwnPropertySymbols.js

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/* Any copyright is dedicated to the Public Domain.

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

assertDeepEq(Object.getOwnPropertySymbols({}), []);

// String keys are ignored.

assertEq(Object.getOwnPropertySymbols({a: 1, b: 2}).length, 0);

assertEq(Object.getOwnPropertySymbols([0, 1, 2, 3]).length, 0);

// Symbol keys are observed.

var iterable = {};

Object.defineProperty(iterable, Symbol.iterator, {

    value: () => [][Symbol.iterator]()

});

assertDeepEq(Object.getOwnPropertySymbols(iterable), [Symbol.iterator]);

assertDeepEq(Object.getOwnPropertySymbols(new Proxy(iterable, {})), [Symbol.iterator]);

// Test on an object with a thousand own properties.

var obj = {};

for (var i = 0; i < 1000; i++) {

    obj[Symbol.for("x" + i)] = 1;

assertEq(Object.getOwnPropertyNames(obj).length, 0);

var symbols = Object.getOwnPropertySymbols(obj);

assertEq(symbols.length, 1000);

assertEq(symbols.indexOf(Symbol.for("x0")) !== -1, true);

assertEq(symbols.indexOf(Symbol.for("x241")) !== -1, true);

assertEq(symbols.indexOf(Symbol.for("x999")) !== -1, true);

assertEq(Object.getOwnPropertySymbols(new Proxy(obj, {})).length, 1000);

// The prototype chain is not consulted.

assertEq(Object.getOwnPropertySymbols(Object.create(obj)).length, 0);

assertEq(Object.getOwnPropertySymbols(new Proxy(Object.create(obj), {})).length, 0);

// Primitives are coerced to objects; but there are never any symbol-keyed

// properties on the resulting wrapper objects.

assertThrowsInstanceOf(() => Object.getOwnPropertySymbols(), TypeError);

assertThrowsInstanceOf(() => Object.getOwnPropertySymbols(undefined), TypeError);

assertThrowsInstanceOf(() => Object.getOwnPropertySymbols(null), TypeError);

for (var primitive of [true, 1, 3.14, "hello", Symbol()])

    assertEq(Object.getOwnPropertySymbols(primitive).length, 0);

assertEq(Object.getOwnPropertySymbols.length, 1);

if (typeof reportCompare === "function")

    reportCompare(0, 0);