How to select an HTML element by class or tag name in JS?
Jul 23, 2025 am 04:01 AMSelecting HTML elements in JavaScript can be achieved in three ways: 1. Use getElementsByClassName to select by class name, return a dynamic HTMLCollection, and you need to write the class name such as 'box', and access the first element through boxes[0]; 2. Use getElementsByTagName to select by tag name, and also return a dynamic HTMLCollection, suitable for batch operations such as modifying all li styles; 3. Use querySelectorAll to select by CSS selector, support more complex selection logic, and return a static NodeList. If you only need the first match, you can use querySelector. When selecting, please note that the class name is added. The tag name is written directly.
Selecting HTML elements in JavaScript is a common requirement by class name or tag name. You can quickly get elements by directly using the built-in method. The key is to choose the appropriate method according to the scene.

Use getElementsByClassName
to select elements by class name
This method can return an HTMLCollection (class array) based on the specified class name, which contains all matching elements.
- Class names should be written in string form
- If there are multiple class names (for example,
<div class="box red"> ), you need to write <code>box red
in full to matchFor example:
const boxes = document.getElementsByClassName('box');
This way you can get all the elements with the class name
box
. If you want to operate only the first one, you can access it likeboxes[0]
.It should be noted that HTMLCollection is "real-time updated", which means that if the DOM changes, it will change as well.
Use
getElementsByTagName
to select elements by tag nameIf you know that you want to choose a tag like
div
,li
ora
, you can directly use the tag name:const listItems = document.getElementsByTagName('li');
Like
getElementsByClassName
, it also returns a dynamic HTMLCollection. Suitable for when you want to operate a certain type of tag in batches, such as uniformly modifying all paragraph text styles.Use
querySelectorAll
to choose more flexiblyIf you want to operate in the CSS selector,
querySelectorAll
is a better choice. It can support class names, tag names and even more complex combinations:const allBoxes = document.querySelectorAll('.box'); // Const by class name allLinks = document.querySelectorAll('a'); // By label
It returns a static NodeList that does not change with the DOM. This is more controllable in some cases.
Tips:
- If you only want the first match, you can use
querySelector
instead ofquerySelectorAll
- Don't forget to add points before the class name
.
- Just write the tag name directly without adding any symbols
Basically these methods. Selecting elements is not complicated but it is easy to write the syntax incorrectly. Especially when class names and tag names are mixed, just pay more attention to the selector format.
- If you only want the first match, you can use
The above is the detailed content of How to select an HTML element by class or tag name in JS?. For more information, please follow other related articles on the PHP Chinese website!

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