JS: Difference of Array vs Array-Like Object

Difference between array and array-like object

• For true array, value of length will automatically change.
• For true array, its parent is Array.prototype. 〔see Prototype and Inheritance〕
• For true array, Array.isArray return true.

// create a array-like object
const xalike = { 0: "a", 1: "b", length: 2 };
xalike[2] = "c";

// length is 3 if true array
console.log(xalike.length === 2);

console.log(Array.isArray(xalike) === false);

// parent is not Array.prototype
console.log(Reflect.getPrototypeOf(xalike) === Object.prototype);

// s------------------------------

// real array
let xra = ["a", "b"];
xra[2] = "c";

console.log(xra.length === 3);

console.log(Array.isArray(xra));

console.log(Reflect.getPrototypeOf(xra) === Array.prototype);