<div class="input-box">
        <input id="code"  placeholder="验证码"/>
        <button id="sendCode" class="pass-item-time-timing" onclick="code(this)">发送验证码</button>
    </div>

function code(obj) {
    obj=$(obj)
    var num = 60;
    var timer = setInterval(function () {
        if (num > 1) {
            num--;
            obj.text(num).attr("disabled", "disabled");
        } else {
            obj.text("发送验证码").removeAttr("disabled");
            clearInterval(timer);
        }

    }, 1000)

};