Edit in JSFiddle

d1 = document.getElementById("d1");
b1 = document.getElementById("b1");

var done = new Event('done');

d1.addEventListener('done', function(){d1.innerHTML = Math.random()});
b1.addEventListener("click", 
                    function(){
                        b1.innerHTML = Math.random();
                        d1.dispatchEvent(done);
                    })

<div id="d1"> </div>
<button id="b1">button</button>