property-inheritance.js

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/* Any copyright is dedicated to the Public Domain.

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

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

function F() {}

var f = new F();

// inherited data property

F.prototype[sym] = "world";

assertEq(sym in f, true);

assertEq(f.hasOwnProperty(sym), false);

assertEq(f[sym], "world");

// shadowing assignment

f[sym] = "kitty";

assertEq(f[sym], "kitty");

assertEq(F.prototype[sym], "world");

// deletion, revealing previously shadowed property

assertEq(delete f[sym], true);

assertEq(f.hasOwnProperty(sym), false);

assertEq(f[sym], "world");

// inherited accessor property

var value = undefined;

Object.defineProperty(F.prototype, sym, {

    configurable: true,

    get: function () { return 23; },

    set: function (v) { value = v; }

});

assertEq(sym in f, true);

assertEq(f.hasOwnProperty(sym), false);

assertEq(f[sym], 23);

f[sym] = "gravity";

assertEq(value, "gravity");

// inherited accessor property with no setter

Object.defineProperty(F.prototype, sym, {

    set: undefined

});

assertThrowsInstanceOf(function () { "use strict"; f[sym] = 0; }, TypeError);

// deeply inherited accessor property

var g = Object.create(f);

for (var i = 0; i < 100; i++)

    g = Object.create(g);

assertEq(g[sym], 23);

if (typeof reportCompare === "function")

    reportCompare(0, 0);