javascript - 为什么单击按钮会触发焦点？

Question

为什么单击按钮也会触发 focus 事件？

如果我有这个

$('button').on('click', function(e){
   console.log('This was a ' + e.type); 
});
$('button').on('focus', function(e){
   console.log('This was a ' + e.type); 
});

和 HTML

<button>Click me</button>

当我单击按钮时，两个事件都会触发...为什么？

http://jsfiddle.net/PACXn/

Answer 1

因为 <button>始终触发焦点事件(当您单击它时)。正如您可以在 http://api.jquery.com/focus/ 中阅读的那样

"The focus event is sent to an element when it gains focus. This event is implicitly applicable to a limited set of elements, such as form elements (<input>, <select>, etc.) and links (<a href>)."