append css class with javascript code example

Example 1: js add class

var element = document.getElementById('element');
element.classList.add('class-1');
element.classList.add('class-2', 'class-3');
element.classList.remove('class-3');

Example 2: javascript add class

// getting the target element
var myElement = document.querySelector('#myElement');

// example for addding some-class to the element
myElement.classList.add('some-class');

// multiple classes can be added like this
myElement.classList.add('one-class', 'one-more-class');

// example for removing any class from the element
myElement.classList.remove('any-class');

Example 3: append css file with javascript

var cssFile = document.createElement('link');
    cssLink1.rel = 'stylesheet';
    cssLink1.href = "styles.css";  // or path for file {themes('/styles/mobile.css')}
    document.head.appendChild(cssFile); // append css to head element