deleteProperty.js - mozsearch

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/* Any copyright is dedicated to the Public Domain.

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

// Reflect.deleteProperty deletes properties.

var obj = {x: 1, y: 2};

assertEq(Reflect.deleteProperty(obj, "x"), true);

assertDeepEq(obj, {y: 2});

var arr = [1, 1, 2, 3, 5];

assertEq(Reflect.deleteProperty(arr, "3"), true);

assertDeepEq(arr, [1, 1, 2, , 5]);

// === Failure and error cases

// Since Reflect.deleteProperty is almost exactly identical to the non-strict

// `delete` operator, there is not much to test that would not be redundant.

// Returns true if no such property exists.

assertEq(Reflect.deleteProperty({}, "q"), true);

// Or if it's inherited.

var proto = {x: 1};

assertEq(Reflect.deleteProperty(Object.create(proto), "x"), true);

assertEq(proto.x, 1);

// Return false if asked to delete a non-configurable property.

var arr = [];

assertEq(Reflect.deleteProperty(arr, "length"), false);

assertEq(arr.hasOwnProperty("length"), true);

assertEq(Reflect.deleteProperty(this, "undefined"), false);

assertEq(this.undefined, void 0);

// Return false if a Proxy's deleteProperty handler returns a false-y value.

var value;

var proxy = new Proxy({}, {

    deleteProperty(t, k) {

        return value;

});

for (value of [true, false, 0, "something", {}]) {

    assertEq(Reflect.deleteProperty(proxy, "q"), !!value);

// If a Proxy's handler method throws, the error is propagated.

proxy = new Proxy({}, {

    deleteProperty(t, k) { throw "vase"; }

});

assertThrowsValue(() => Reflect.deleteProperty(proxy, "prop"), "vase");

// Throw a TypeError if a Proxy's handler method returns true in violation of

// the object invariants.

proxy = new Proxy(Object.freeze({prop: 1}), {

    deleteProperty(t, k) { return true; }

});

assertThrowsInstanceOf(() => Reflect.deleteProperty(proxy, "prop"), TypeError);

// === Deleting elements from `arguments`

// Non-strict arguments element becomes unmapped

function f(x, y, z) {

    assertEq(Reflect.deleteProperty(arguments, "0"), true);

    arguments.x = 33;

    return x;

assertEq(f(17, 19, 23), 17);

// Frozen non-strict arguments element

function testFrozenArguments() {

    Object.freeze(arguments);

    assertEq(Reflect.deleteProperty(arguments, "0"), false);

    assertEq(arguments[0], "zero");

    assertEq(arguments[1], "one");

testFrozenArguments("zero", "one");

// For more Reflect.deleteProperty tests, see target.js and propertyKeys.js.

reportCompare(0, 0);