DOMTokenList

`Element.classList.add`

Adds the given tokens to the element's class list

Syntax

JavaScript

element.classList.add(...tokens)

Parameters

Parameter	Type	Description
tokens	...string[]	One or more class names to add

Return Value

undefined

Examples

Basic Usage

const el = document.querySelector('.box')!
el.classList.add('active')
el.classList.add('visible', 'animated')

Practical Example

function highlight(id: string) {
  const el = document.getElementById(id)
  el?.classList.add('highlight', 'pulse')
}

Advanced Usage

document.querySelectorAll('tr:nth-child(even)').forEach(row => {
  row.classList.add('striped')
})

Understanding Element.classList.add

The Element.classList.add method in JavaScript adds the given tokens to the element's class list. It belongs to the DOMTokenList object and is one of the most widely used methods for working with domtokenlist values in modern JavaScript and TypeScript applications.

The method signature is element.classList.add(...tokens). It accepts 1 parameter: tokens. When called, it returns undefined. Understanding when and how to use add() helps you write more expressive, readable code.

Common use cases for Element.classList.add include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like dom-classlist-remove, dom-classlist-toggle, dom-classlist-contains, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for Element.classList.add is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.