JavaScript: Set Object

By Xah Lee. Date: . Last updated: .

New in JS2015.

Set is the value of the property key "Set" of the Global Object .

console.log( window.Set === Set );

Type

Type of Set is a function.

console.log( typeof Set === "function" );

Parent

Parent of Set is Function.prototype.

console.log( Reflect.getPrototypeOf ( Set ) === Function.prototype );

Purpose

Purpose of Set is:

“Set” objects are collections of values.

How Set Determines Uniqueness

The equality test used for determining whether 2 values in a set is the same as ===, except treatment of NaN (not a number).

NaN === NaN return false, but for set object, NaN is considered same as any NaN.

// equality test used for determining whether 2 values in the set is the same as ===, except treatment of NaN

// NaN === NaN is false
console.log((NaN === NaN) === false);

// but for set object, NaN is same as any NaN
const ss = new Set([NaN, NaN]);
console.log(ss.size === 1);

Set Constructor

Set Constructor

Properties

JavaScript Set Object

BUY
ΣJS
JavaScript in Depth

JS Obj Reference

Set

prototype