JSTests/stress/builtin-function-length.js

function shouldBe(actual, expected) {
    if (actual !== expected)
        throw new Error('bad value: ' + actual);
}

function shouldThrow(func, errorMessage) {
    var errorThrown = false;
    var error = null;
    try {
        func();
    } catch (e) {
        errorThrown = true;
        error = e;
    }
    if (!errorThrown)
        throw new Error('not thrown');
    if (String(error) !== errorMessage)
        throw new Error(`bad error: ${String(error)}`);
}

{
    shouldBe(JSON.stringify(Object.getOwnPropertyNames(Array.prototype.filter).sort()), `["length","name"]`);
    shouldBe(Array.prototype.filter.length, 1);
    shouldBe(JSON.stringify(Object.getOwnPropertyDescriptor(Array.prototype.filter, 'length')), `{"value":1,"writable":false,"enumerable":false,"configurable":true}`);
    shouldBe(delete Array.prototype.filter.length, true);
    shouldBe(JSON.stringify(Object.getOwnPropertyNames(Array.prototype.filter).sort()), `["name"]`);
}

{
    shouldThrow(function () {
        "use strict";
        Array.prototype.forEach.length = 42;
    }, `TypeError: Attempted to assign to readonly property.`);
}

{
    var resolve = null;
    var reject = null;
    new Promise(function (arg0, arg1) {
        resolve = arg0;
        reject = arg1;
    });
    shouldBe(resolve.length, 1);
    shouldBe(JSON.stringify(Object.getOwnPropertyDescriptor(resolve, 'length')), `{"value":1,"writable":false,"enumerable":false,"configurable":true}`);
    shouldBe(reject.length, 1);
    shouldBe(JSON.stringify(Object.getOwnPropertyDescriptor(reject, 'length')), `{"value":1,"writable":false,"enumerable":false,"configurable":true}`);
}