Answers for "add function to existing class javascript"

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');

js 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');