How to add onclick to a html element dynamically using javascript -

i able create button element , add onclick event shown below.

elem.onclick=function() { alert("qweqweqwe"); }

how go using predefined function instead of defining function inside of event? like:

elem.onclick=func();

add eventlistener element has defined function call :

elem.addeventlistener("click", func, false); //where func function name

Silver