事件模仿
$(function(){
$('#old').bind("click", function(){
$("input").trigger("focus");
});
$('#new').bind("click", function(){
$("input").triggerHandler("focus");
});
$("input").focus(function(){
$("body").append("<p>focus.</p>");
})
})


<button id="old">trigger</button>
<button id="new">triggerHandler</button>
<input />