JS: Array-Like Object

What is a array-like object

A object such that Array.isArray(obj) returns false.

typically, array-like object is a normal data object with a length property, and property keys of 0, 1, 2 etc, so it looks like an array.

typically the "length" property has the Enumerable attribute false.

Create a array-like object

// simplest array-like object
let xx = { length: 2 };
console.log(xx);
// { length: 2 }

// create array-like object
let xx = { 0: "a", 1: "b", length: 2 };

// optional
Reflect.defineProperty(xx, "length", { enumerable: false });

console.log(xx);
// { "0": "a", "1": "b" }

Difference between array vs array-like object

• JS: Difference of Array vs Array-Like Object

Check if a object is true array

• JS: Array.isArray

Where does array-like object came from

• the arguments object is a array-like object.
• In web browser, method such as document.getElementsByClassName return array-like objects. [see Get Element by ID, Name, Class etc]
• new String("abc") creates a array-like object. [see String Constructor]

Convert array-like object to array

• JS: Convert Array-Like Object to Array

Array-like object is a major wart in javascript

It is a JavaScript design warts.

whenever you see it, best is to convert it to true array right away.

Get property values of array-like object

• JS: List Properties (to array)