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Other References

CSSStyleDeclaration JS Conversion


HTML DOM Element className

Example

Set the class attribute for an element:

element.className = "myStyle";
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Get the class attribute of "myDIV":

let value = document.getElementById("myDIV").className;
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Toggle between two class names:

if (element.className == "myStyle") {
  element.className = "newStyle";
} else {
  element.className = "myStyle";
}
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More examples below.


Definition and Usage

The className property sets or returns an element's class attribute.


Syntax

Return the className property:

HTMLElementObject.className

Set the className property:

HTMLElementObject.className = class

Property Values

Value Description
class The class name(s) of an element.
Separate multiple classes with spaces, like "test demo".


Return Value

Type Description
StringThe class, or a space-separated list of classes, of an element

More Examples

Get the class attribute of the first <div> element (if any):

let value = document.getElementsByTagName("div")[0].className;
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Get a class attribute with multiple classes:

<div id="myDIV" class="myStyle test example">
<p>I am myDIV.</p>
</div>
let value = document.getElementById("myDIV").className;
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Overwrite an existing class attribute with a new one:

element.className = "newClassName";
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To add new classes, without overwriting existing values, add a space and the new classes:

element.className += " class1 class2";
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if "myDIV" has a "myStyle" class, change the font size:

const elem = document.getElementById("myDIV");

if (elem.className == "mystyle") {
  elem.style.fontSize = "30px";
}
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If you scroll 50 pixels from the top of this page, the class "test" is added:

window.onscroll = function() {myFunction()};

function myFunction() {
  if (document.body.scrollTop > 50) {
    document.getElementById("myP").className = "test";
  } else {
    document.getElementById("myP").className = "";
  }
}
Try it Yourself »

Related Pages

CSS Tutorial: CSS Syntax

CSS Reference: CSS .class Selector


Browser Support

element.className is supported in all browsers:

Chrome IE Edge Firefox Safari Opera
Yes Yes Yes Yes Yes Yes