object-assign.js - mozsearch

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function test() {

    var from, to;

    // Property changes value.

    from = {x: 1, y: 2};

    to = {set x(v) { from.y = 5; }};

    Object.assign(to, from);

    assertEq(to.y, 5);

    // Property becomes a getter.

    from = {x: 1, y: 2};

    to = {set x(v) { Object.defineProperty(from, "y", {get: () => 4}); }};

    Object.assign(to, from);

    assertEq(to.y, 4);

    // Property becomes non-enumerable.

    from = {x: 1, y: 2};

    to = {set x(v) { Object.defineProperty(from, "y", {value: 2,

						       enumerable: false,

						       configurable: true,

						       writable: true}); }};

    Object.assign(to, from);

    assertEq("y" in to, false);

    to = {};

    Object.assign(to, from);

    assertEq("y" in to, false);

    // Property is deleted. Should NOT get Object.prototype.toString.

    from = {x: 1, toString: 2};

    to = {set x(v) { delete from.toString; }};

    Object.assign(to, from);

    assertEq(to.hasOwnProperty("toString"), false);

    from = {toString: 2, x: 1};

    to = {set x(v) { delete from.toString; }};

    Object.assign(to, from);

    assertEq(to.toString, 2);

    from = {x: 1, toString: 2, y: 3};

    to = {set x(v) { delete from.toString; }};

    Object.assign(to, from);

    assertEq(to.hasOwnProperty("toString"), false);

    assertEq(to.y, 3);

    // New property is added.

    from = {x: 1, y: 2};

    to = {set x(v) { from.z = 3; }};

    Object.assign(to, from);

    assertEq("z" in to, false);

    // From getter.

    var c = 7;

    from = {x: 1, get y() { return ++c; }};

    to = {};

    Object.assign(to, from);

    Object.assign(to, from, from);

    assertEq(to.y, 10);

    // Frozen object.

    from = {x: 1, y: 2};

    to = {x: 4};

    Object.freeze(to);

    var ex;

    try {

	Object.assign(to, from);

    } catch (e) {

	ex = e;

    assertEq(ex instanceof TypeError, true);

    assertEq(to.x, 4);

    // Non-writable property.

    from = {x: 1, y: 2, z: 3};

    to = {};

    Object.defineProperty(to, "y", {value: 9, writable: false});

    ex = null;

    try {

	Object.assign(to, from);

    } catch(e) {

	ex = e;

    assertEq(ex instanceof TypeError, true);

    assertEq(to.x, 1);

    assertEq(to.y, 9);

    assertEq(to.z, undefined);

    // Array with dense elements.

    from = [1, 2, 3];

    to = {};

    Object.assign(to, from);

    assertEq(to[2], 3);

    assertEq("length" in to, false);

    // Object with sparse elements and symbols.

    from = {x: 1, 1234567: 2,  1234560: 3,[Symbol.iterator]: 5, z: 3};

    to = {};

    Object.assign(to, from);

    assertEq(to[1234567], 2);

    assertEq(Object.keys(to).toString(), "1234560,1234567,x,z");

    assertEq(to[Symbol.iterator], 5);

    // Symbol properties need to be assigned last.

    from = {x: 1, [Symbol.iterator]: 2, y: 3};

    to = {set y(v) { throw 9; }};

    ex = null;

    try {

	Object.assign(to, from);

    } catch (e) {

	ex = e;

    assertEq(ex, 9);

    assertEq(to.x, 1);

    assertEq(to.hasOwnProperty(Symbol.iterator), false);

    // Typed array.

    from = new Int32Array([1, 2, 3]);

    to = {};

    Object.assign(to, from);

    assertEq(to[1], 2);

    // Primitive string.

    from = "foo";

    to = {};

    Object.assign(to, from);

    assertEq(to[0], "f");

    // String object.

    from = new String("bar");

    to = {};

    Object.assign(to, from);

    assertEq(to[2], "r");

test();

test();

test();