property-nonwritable.js

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/* Any copyright is dedicated to the Public Domain.

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

var sym = Symbol.for("moon");

function checkNotWritable(obj) {

    // In sloppy mode, assigning to a nonwritable property silently fails.

    obj[sym] = "portals";

    assertEq(obj[sym], "cheese");

    // In strict mode code, it throws.

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

    assertEq(obj[sym], "cheese");

var x = {};

Object.defineProperty(x, sym, {

    configurable: true,

    enumerable: true,

    value: "cheese",

    writable: false

});

checkNotWritable(x);

// Assignment can't shadow inherited nonwritable properties either.

var y = Object.create(x);

checkNotWritable(y);

checkNotWritable(Object.create(y));

if (typeof reportCompare === "function")

    reportCompare(0, 0);