classList is a JavaScript property that can be used to work with CSS classes on HTML elements, useful to add, remove, replace and toggle CSS classes on an element. It contains an object list of the class attribute.
Syntax:
element.classList
- If the class attribute was not set or is empty, the element.classList.length returns 0.

classList Methods

The object contained by the classList property has these methods:

classList Examples

1. Add two css classes to a <div>:
var div1 = document.getElementById('div1');
div1.classList.add('cls_1', 'cls_2');
2. Remove a css class from a <div>:
var div1 = document.getElementById('div1');
div1.classList.remove('cls_2');
3. Check if a <div> contains or not a specified css class:
var div1 = document.getElementById('div1');
if(div1.classList.contains('cls_1')) alert('.cls_1 in #div1');
else alert('.cls_1 not in #div1');
4. Replace class 'foo' with 'bar':
var div1 = document.getElementById('div1');
div1.classList.replace('foo', 'bar');
5. If 'visible' is set remove it, otherwise add it:
var div1 = document.getElementById('div1');
div1.classList.toggle('visible');

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which tag is used in <table> to create table header cell?
<thead> <th> <td>
<table><tr>
  <th>Title 1</th>
  <th>Title 2</th>
</tr></table>
Which CSS property sets the distance between lines?
line-height word-spacing margin
.some_class {
  line-height: 150%;
}
Which function opens a new browser window.
alert() confirm() open()
document.getElementById("id_button").onclick = function(){
  window.open("http://coursesweb.net/");
}
Indicate the PHP function that returns an array with names of the files and folders inside a directory.
mkdir() scandir() readdir()
$ar_dir = scandir("dir_name");
var_export($ar_dir);
classList - Working with CSS classes

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