from_this.js - mozsearch

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/* Any copyright is dedicated to the Public Domain.

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

// The third argument to Array.from is passed as the 'this' value to the

// mapping function.

var hits = 0, obj = {};

function f(x) {

    assertEq(this, obj);

    hits++;

Array.from(["a", "b", "c"], f, obj);

assertEq(hits, 3);

// Without an argument, undefined is passed...

hits = 0;

function gs(x) {

    "use strict";

    assertEq(this, undefined);

    hits++;

Array.from("def", gs);

assertEq(hits, 3);

// ...and if the mapping function is non-strict, that means the global is

// passed.

var global = this;

hits = 0;

function g(x) {

    assertEq(this, global);

    hits++;

Array.from("ghi", g);

assertEq(hits, 3);

// A primitive value can be passed.

for (var v of [0, "str", undefined]) {

    hits = 0;

    var mapfn = function h(x) {

        "use strict";

        assertEq(this, v);

        hits++;

};

    Array.from("pq", mapfn, v);

    assertEq(hits, 2);

if (typeof reportCompare === 'function')

    reportCompare(0, 0);