点击按钮60秒倒计时js代码

直接上代码：

<input type="button" id="btn" value="免费获取验证码" onclick="settime(this)" /> 
<script type="text/JavaScript"> 
var countdown=60;  
function settime(val) {  
    if (countdown == 0) {  
        val.removeAttribute("disabled");     
        val.value="免费获取验证码";  
        countdown = 60;  
    } else {  
        val.setAttribute("disabled", true);  
        val.value="重新发送(" + countdown + ")";  
        countdown--;  
    }  
    setTimeout(function() {  
    settime(val)  
    },1000)  
}  
</script>