javascript button handler code example

Example 1: how to add onclick event in javascript

var element = document.getElementById("elem");
element.onclick = function(event) {
  console.log(event);
}

Example 2: onclick a tag

<a href='http://www.google.com' onclick='return check()'>check</a>

<script type='text/javascript'>
function check() {
    return false;
}
</script>