30-seconds-of-code/blog_posts/javascript-store-dom-items.md

title, shortTitle, type, tags, expertise, author, cover, excerpt, firstSeen, lastUpdated

title	shortTitle	type	tags	expertise	author	cover	excerpt	firstSeen	lastUpdated
Tip: Minimize DOM access	Minimize DOM access	tip	javascript,browser	intermediate	chalarangelo	blog_images/armchair.jpg	Increase your JavaScript code's performance when working with the DOM by leveraging this simple trick.	2020-11-20T09:18:55+02:00	2021-06-12T19:30:41+03:00

DOM operations, including accessing the DOM, are generally slow. This is usually not a problem until you have to perform many DOM operations and your JavaScript application's performance starts to suffer. A very quick trick to increase performance is to store DOM elements or their values in local variables if you plan to access them multiple times.

// This is slow, it accesses the DOM element multiple times
document.querySelector('#my-element').classList.add('my-class');
document.querySelector('#my-element').textContent = 'hello';
document.querySelector('#my-element').hidden = false;

// This is faster, it stores the DOM element in a variable
const myElement = document.querySelector('#my-element');
myElement.classList.add('my-class');
myElement.textContent = 'hello';
myElement.hidden = false;

Note that, while this trick may come in handy, it comes with the caveat that if you later remove the DOM element and you still have it stored in a variable, the variable should be set to null to avoid potential memory leaks.