Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript and the DOM (Retiring) Getting a Handle on the DOM Selecting Multiple Elements

Daniel Springer
PLUS
Daniel Springer
Courses Plus Student 5,090 Points
Posted by Daniel Springer
Daniel Springer
Courses Plus Student 5,090 Points

I found 3 possible answers. But which one is the right one in this case?

let listItems = document.getElementsByTagName('li')

or

let listItems = document.querySelectorAll('li')

or 

let listItems = document.querySelectorAll("#rainbow li");
index.html 
<!DOCTYPE html>
<html>
  <head>
    <title>Rainbow!</title>
  </head>
  <body>
    <ul id="rainbow">
      <li>This should be red</li>
      <li>This should be orange</li>
      <li>This should be yellow</li>
      <li>This should be green</li>
      <li>This should be blue</li>
      <li>This should be indigo</li>
      <li>This should be violet</li>
    </ul>
    <script src="js/app.js"></script>
  </body>
</html>
js/app.js 
let listItems;
const colors = ["#C2272D", "#F8931F", "#FFFF01", "#009245", "#0193D9", "#0C04ED", "#612F90"];

for(var i = 0; i < colors.length; i ++) {
  listItems[i].style.color = colors[i];    
}

2 Answers

Matt Brock
Matt Brock
28,330 Points

I'd use the getElementsByTagName() method, as it is MUCH more performant in this case (see this jsperf test). querySelectorAll() has more flexibility and can use any selector. A general rule of thumb would be:

  • Use getElementsByTagName() when you're searching for groups of elements (<li>, <a>, etc.)
  • Use querySelectorAll() when you're searching for groups of complex selectors (.element .child, #rainbow li, etc.)

Here's a good breakdown to read through.

Matt Brock
Matt Brock
28,330 Points

Another huge difference is what the two methods return when called. getElementsByTagName() returns a live list of HTML nodes that are updated as content within them changes. querySelectorAll(), however, returns a non-live list of HTML nodes, or static NodeList, that is not updated with content changes. Check out the MDN Docs on NodeList to read about the two: https://developer.mozilla.org/en-US/docs/Web/API/NodeList.

Matt Brock
Matt Brock
28,330 Points

You're so welcome :)