Why the onclick element will trigger twice for label element

Answer 1

The Label tag will be associated with the input tag inside it. So when you click the label, it will also trigger a click event for the input, then bubble to the label itself.

See this:

document.getElementById("winput").addEventListener('click', function(event){
     alert('input click');

     //stop bubble
     event.stopPropagation();

 }, false); 

http://jsfiddle.net/96vPP/