The Selectors API: querySelector and querySelectorAll

• Introduction
• The Selectors API
• Basic jQuery to DOM API examples
  • Select by id
  • Select by class
  • Select by tag name
• More advanced jQuery to DOM API examples
  • Select multiple items
  • Select by HTML attribute value
  • Select by CSS pseudo class
  • Select the descendants of an element

Introduction

jQuery and other DOM libraries got a huge popularity boost in the past, among with the other features they provided, thanks to an easy way to select elements on a page.

Traditionally browsers provided just a single way to select a DOM element - by its id attribute, with getElementById(), a method offered by the document object.

The Selectors API

Since 2013 the Selectors API, the DOM allows you to use two more useful methods:

• document.querySelector()
• document.querySelectorAll()

They can be safely used, as caniuse.com tells us, and they are even fully supported on IE9 in addition to all the other modern browsers, so there is no reason to avoid them, unless you need to support IE8 (which has partial support) and below.

They accept any CSS selector, so you are no longer limited by selecting elements by id.

• document.querySelector() returns a single element, the first found
• document.querySelectorAll() returns all the elements, wrapped in a NodeList object.

These are all valid selectors:

• document.querySelector('#test')
• document.querySelector('.my-class')
• document.querySelector('#test .my-class')
• document.querySelector('a:hover')

Basic jQuery to DOM API examples

Here below is a translation of the popular jQuery API into native DOM API calls.

Select by id

$('#test')
document.querySelector('#test')

We use querySelector since an id is unique in the page

Select by class

$('.test')
document.querySelectorAll('.test')

Select by tag name

$('div')
document.querySelectorAll('div')

More advanced jQuery to DOM API examples

Select multiple items

$('div, span')
document.querySelectorAll('div, span')

Select by HTML attribute value

$('[data-example="test"]')
document.querySelectorAll('[data-example="test"]')

Select by CSS pseudo class

$(':nth-child(4n)')
document.querySelectorAll(':nth-child(4n)')

Select the descendants of an element

For example all li elements under #test:

$('#test li')
document.querySelectorAll('#test li')