js 倒计时按钮可用

HTML

  <a class="btn btn-default" id="enterBtn" disabled  style="margin-top:2rem" href="legalnewform.html">
       已知晓，进入法律咨询<span id="countDown" style="float:right">(5)</span>
  </a>

JS

 <script type="text/javascript">
      
        window.setTimeout("CountDown()", 1000);

        function CountDown() {

            var span = document.getElementById("countDown");

            //改变span里面的值  
            var r = /[0-9]+/g;
            var a = span.innerText.match(r);
            span.innerText = "("+ ( a - 1)+")";

            //判断是否减到了0

            if (span.innerText == "(0)") {

                document.getElementById("enterBtn").removeAttribute("disabled");
                span.innerText = "";
                return;

            }

            window.setTimeout("CountDown()", 1000);

        }
    </script>

效果截图