How to set CSS3 transition using javascript?

Question

How can I set CSS using javascript (I don\'t have access to the CSS file)?

#fade div {
  -webkit-transition: opacity 1s;
  -moz-transition: opacity 1s;
  -o-         


        

Answer 1

function reg(){

var style = document.head.appendChild(document.createElement("style"));

style.innerHTML = "#main:after {border-right:400px solid #fde561; left:0 ; transition : 0.5s all ease}";

}