Array-of-length-setter.js

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// Array.of calls a "length" setter if one is present.

var hits = 0;

var lastObj = null, lastVal = undefined;

function setter(v) {

    hits++;

    lastObj = this;

    lastVal = v;

// when the setter is on the new object

function Pack() {

    Object.defineProperty(this, "length", {set: setter});

Pack.of = Array.of;

var pack = Pack.of("wolves", "cards", "cigarettes", "lies");

assertEq(lastObj, pack);

assertEq(lastVal, 4);

// when the setter is on the new object's prototype

function Bevy() {}

Object.defineProperty(Bevy.prototype, "length", {set: setter});

Bevy.of = Array.of;

var bevy = Bevy.of("quail");

assertEq(lastObj, bevy);

assertEq(lastVal, 1);