how to make event in js

chaychu = document.getElementById('chaychu');
chaychu.onMouseOver ="chaychu.stop";

How to make this code works- what is wrong开发者_C百科 with it?

You need to wrap it in function body:

chaychu = document.getElementById('chaychu');
chaychu.onmouseover = function(){
    // your code here....
};

If there is a function already there, you should do this instead:

chaychu = document.getElementById('chaychu');
chaychu.onmouseover = functionName;