jquery 发送验证码60s倒计时，后重新发送

#html
<div class="user_code">
    <input type="text" placeholder="请输入验证码" name="code" >
    <input type="button" class="getCode"  value="发送">
</div>



#js
var countdown=60;
send=function(obj){
	if (countdown == 0) {
		obj.removeAttr('disabled');
		obj.attr('value','发送');
		countdown = 60;
		return;
	} else {
		obj.attr('disabled','disabled');
		obj.attr('value',"重新发送(" + countdown + ")");
		countdown--;
	}
	setTimeout(function() {
			send(obj) }
		,1000)
}