how to append a css class to an element by javascript?

Question

Suppose a HTML element\'s id is known, so the element can be refereced using:

document.getElementById(element_id);

Does a nati

Answer 1

When an element already has a class name defined, its influence on the element is tied to its position in the string of class names. Later classes override earlier ones, if there is a conflict.

Adding a class to an element ought to move the class name to the sharp end of the list, if it exists already.

document.addClass= function(el, css){
    var tem, C= el.className.split(/\s+/), A=[];    
    while(C.length){
        tem= C.shift();
        if(tem && tem!= css) A[A.length]= tem;
    }
    A[A.length]= css;
    return el.className= A.join(' ');   
}