How do I add a class to a given element?

Question

I have an element that already has a class:

Answer 1

You can use the API querySelector to select your element and then create a function with the element and the new classname as parameters. Using classlist for modern browsers, else for IE8. Then you can call the function after an event.

 //select the dom element
 var addClassVar = document.querySelector('.someclass');

 //define the addclass function
 var addClass = function(el,className){
   if (el.classList){
     el.classList.add(className);
   }
   else {
     el.className += ' ' + className;
  }
};

//call the function
addClass(addClassVar, 'newClass');