[javascript] JavaScript CSS how to add and remove multiple CSS classes to an element

How can assign multiple css classes to an html element through javascript without using any libraries?

ClassList add

var dynamic=document.getElementById("dynamic");
dynamic.classList.add("red");
dynamic.classList.add("size");
dynamic.classList.add("bold");

.red{
color:red;
}
.size{
font-size:40px;
}
.bold{
font-weight:800;
}

<div id="dynamic">dynamic css</div>

just use this

element.getAttributeNode("class").value += " antherClass";

take care about Space to avoid mix old class with new class

the Element.className += " MyClass"; is not recommended approach because it will always add these classes whether they were exit or not.

in my case, I was uploading an image file and adding classes to it, now with this each time you upload an image it will add these class whether they exist or not,

the recommended way is Element.classList.add("class1" , "class2" , "class3"); this way will not add extra classes if they already there.

Since I could not find this answer nowhere:

ES6 way (Modern Browsers)

el.classList.add("foo", "bar", "baz");

You can add and remove multiple classes in same way with different in-built methods:

const myElem = document.getElementById('element-id');
//add multiple classes
myElem.classList.add('class-one', 'class-two', 'class-three');
//remove multiple classes
myElem.classList.remove('class-one', 'class-two', 'class-three');

Perhaps:

document.getElementById("myEle").className = "class1 class2";

Not tested, but should work.

Try this:

function addClass(element, value) {
  if(!element.className) {
    element.className = value;
  } else {
    newClassName = element.className;
    newClassName+= " ";
    newClassName+= value;
    element.className = newClassName;
  }
}

Similar logic could be used to make a removeClass function.

guaranteed to work on new browsers. the old className way may not, since it's deprecated.

<element class="oneclass" />

element.setAttribute('class', element.getAttribute('class') + ' another');
alert(element.getAttribute('class')); // oneclass another

In modern browsers, the classList API is supported.

This allows for a (vanilla) JavaScript function like this:

var addClasses;

addClasses = function (selector, classArray) {
    'use strict';

    var className, element, elements, i, j, lengthI, lengthJ;

    elements = document.querySelectorAll(selector);

    // Loop through the elements
    for (i = 0, lengthI = elements.length; i < lengthI; i += 1) {
        element = elements[i];

        // Loop through the array of classes to add one class at a time
        for (j = 0, lengthJ = classArray.length; j < lengthJ; j += 1) {
            className = classArray[j];

            element.classList.add(className);
        }
    }
};

Modern browsers (not IE) support passing multiple arguments to the classList::add function, which would remove the need for the nested loop, simplifying the function a bit:

var addClasses;

addClasses = function (selector, classArray) {
    'use strict';

    var classList, className, element, elements, i, j, lengthI, lengthJ;

    elements = document.querySelectorAll(selector);

    // Loop through the elements
    for (i = 0, lengthI = elements.length; i < lengthI; i += 1) {
        element = elements[i];
        classList = element.classList;

        // Pass the array of classes as multiple arguments to classList::add
        classList.add.apply(classList, classArray);
    }
};

Usage

addClasses('.button', ['large', 'primary']);

Functional version

var addClassesToElement, addClassesToSelection;

addClassesToElement = function (element, classArray) {
    'use strict';

    classArray.forEach(function (className) {
       element.classList.add(className);
    });
};

addClassesToSelection = function (selector, classArray) {
    'use strict';

    // Use Array::forEach on NodeList to iterate over results.
    // Okay, since we’re not trying to modify the NodeList.
    Array.prototype.forEach.call(document.querySelectorAll(selector), function (element) {
        addClassesToElement(element, classArray)
    });
};

// Usage
addClassesToSelection('.button', ['button', 'button--primary', 'button--large'])

The classList::add function will prevent multiple instances of the same CSS class as opposed to some of the previous answers.

Resources on the classList API:

• Can I use
• MDN
• David Walsh
• HTML5 Doctor

Maybe this will help you learn:

//<![CDATA[_x000D_
/* external.js */_x000D_
var doc, bod, htm, C, E, addClassName, removeClassName; // for use onload elsewhere_x000D_
addEventListener('load', function(){_x000D_
doc = document; bod = doc.body; htm = doc.documentElement;_x000D_
C = function(tag){_x000D_
  return doc.createElement(tag);_x000D_
}_x000D_
E = function(id){_x000D_
  return doc.getElementById(id);_x000D_
}_x000D_
addClassName = function(element, className){_x000D_
  var rx = new RegExp('^(.+\s)*'+className+'(\s.+)*$');_x000D_
  if(!element.className.match(rx)){_x000D_
    element.className += ' '+className;_x000D_
  }_x000D_
  return element.className;_x000D_
}_x000D_
removeClassName = function(element, className){_x000D_
  element.className = element.className.replace(new RegExp('\s?'+className), '');_x000D_
  return element.className;_x000D_
}_x000D_
var out = E('output'), mn = doc.getElementsByClassName('main')[0];_x000D_
out.innerHTML = addClassName(mn, 'wow');_x000D_
out.innerHTML = addClassName(mn, 'cool');_x000D_
out.innerHTML = addClassName(mn, 'it works');_x000D_
out.innerHTML = removeClassName(mn, 'wow');_x000D_
out.innerHTML = removeClassName(mn, 'main');_x000D_
_x000D_
}); // close load_x000D_
//]]>

/* external.css */_x000D_
html,body{_x000D_
  padding:0; margin:0;_x000D_
}_x000D_
.main{_x000D_
  width:980px; margin:0 auto;_x000D_
}

<!DOCTYPE html>_x000D_
<html xmlns='http://www.w3.org/1999/xhtml' xml:lang='en' lang='en'>_x000D_
  <head>_x000D_
    <meta http-equiv='content-type' content='text/html;charset=utf-8' />_x000D_
    <link type='text/css' rel='stylesheet' href='external.css' />_x000D_
    <script type='text/javascript' src='external.js'></script>_x000D_
  </head>_x000D_
<body>_x000D_
  <div class='main'>_x000D_
    <div id='output'></div>_x000D_
  </div>_x000D_
</body>_x000D_
</html>

2 great ways to ADD:

But the first way is more cleaner, since for the second you have to add a space at the beginning. This is to avoid the class name from joining with the previous class.

element.classList.add("d-flex", "align-items-center");
element.className += " d-flex align-items-center";

Then to REMOVE use the cleaner way, by use of classList

element.classList.remove("d-grid", "bg-danger");

  addClass(element, className1, className2){
    element.classList.add(className1, className2);
  }
  removeClass(element, className1, className2) {
    element.classList.remove(className1, className2);
  }

removeClass(myElement, 'myClass1', 'myClass2');
addClass(myElement, 'myClass1', 'myClass2');

This works:

myElement.className = 'foo bar baz';

Here's a simpler method to add multiple classes via classList (supported by all modern browsers, as noted in other answers here):

div.classList.add('foo', 'bar'); // add multiple classes

From: https://developer.mozilla.org/en-US/docs/Web/API/Element/classList#Examples

If you have an array of class names to add to an element, you can use the ES6 spread operator to pass them all into classList.add() via this one-liner:

let classesToAdd = [ 'foo', 'bar', 'baz' ];
div.classList.add(...classesToAdd);

Note that not all browsers support ES6 natively yet, so as with any other ES6 answer you'll probably want to use a transpiler like Babel, or just stick with ES5 and use a solution like @LayZee's above.

There are at least a few different ways:

var buttonTop = document.getElementById("buttonTop");

buttonTop.className = "myElement myButton myStyle";

buttonTop.className = "myElement";

buttonTop.className += " myButton myStyle";

buttonTop.classList.add("myElement");

buttonTop.classList.add("myButton", "myStyle");

buttonTop.setAttribute("class", "myElement");

buttonTop.setAttribute("class", buttonTop.getAttribute("class") + " myButton myStyle");

buttonTop.classList.remove("myElement", "myButton", "myStyle");

var el = document.getElementsByClassName('myclass')

el[0].classList.add('newclass');

el[0].classList.remove('newclass');

To find whether the class exists or not, use:

el[0].classList.contains('newclass'); // this will return true or false 

Browser support IE8+