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describe("errors", () => {
test("invalid array length value", () => {
var a = [1, 2, 3];
[undefined, "foo", -1, Infinity, -Infinity, NaN].forEach(value => {
expect(() => {
a.length = value;
}).toThrowWithMessage(RangeError, "Invalid array length");
expect(a).toHaveLength(3);
});
});
});
describe("normal behavior", () => {
test("extend array by setting length", () => {
var a = [1, 2, 3];
a.length = 5;
expect(a).toEqual([1, 2, 3, undefined, undefined]);
});
test("truncate array by setting length", () => {
var a = [1, 2, 3];
a.length = 2;
expect(a).toEqual([1, 2]);
a.length = 0;
expect(a).toEqual([]);
});
test("length value is coerced to number if possible", () => {
var a = [1, 2, 3];
a.length = "42";
expect(a).toHaveLength(42);
a.length = [];
expect(a).toHaveLength(0);
a.length = true;
expect(a).toHaveLength(1);
});
test("setting a huge array length", () => {
var a = [];
a.length = 0x80000000;
expect(a.length).toEqual(0x80000000);
var b = [];
b.length = 0x80000001;
expect(b.length).toEqual(0x80000001);
});
test("should not remove non-configurable values", () => {
var a = [1, undefined, 3];
Object.defineProperty(a, 1, { configurable: false, value: 2 });
expect(a.length).toEqual(3);
expect((a.length = 1)).toEqual(1);
expect(a.length).toEqual(2);
expect(a[1]).toEqual(2);
});
});
describe("behavior when obj has Array prototype", () => {
function ArrExtend() {}
ArrExtend.prototype = [10, 11, 12];
test("Has the properties from prototype", () => {
var arr = new ArrExtend();
expect(arr.length).toEqual(3);
expect(arr[0]).toEqual(10);
expect(arr[1]).toEqual(11);
expect(arr[2]).toEqual(12);
});
test("Can override length to any value", () => {
[null, "Hello friends :^)", -6, 0].forEach(value => {
var arr = new ArrExtend();
arr.length = value;
expect(arr.length).toEqual(value);
// should not wipe high values
expect(arr[0]).toEqual(10);
expect(arr[1]).toEqual(11);
expect(arr[2]).toEqual(12);
});
});
test("Can call array methods", () => {
var arr = new ArrExtend();
arr.push(1);
expect(arr.length).toEqual(4);
expect(arr[3]).toEqual(1);
});
test("If length overwritten uses that value", () => {
[null, "Hello friends :^)", -6, 0].forEach(value => {
var arr = new ArrExtend();
arr.length = value;
expect(arr.length).toEqual(value);
arr.push(99);
expect(arr.length).toEqual(1);
expect(arr[0]).toEqual(99);
// should not wipe higher value
expect(arr[1]).toEqual(11);
expect(arr[2]).toEqual(12);
arr.push(100);
expect(arr.length).toEqual(2);
expect(arr[1]).toEqual(100);
arr.length = 0;
// should not wipe values since we are not an array
expect(arr[0]).toEqual(99);
expect(arr[1]).toEqual(100);
expect(arr[2]).toEqual(12);
});
});
});
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