JS判断字符串是否为纯数字

写法一：

<script type="text/javascript">function checknum(){ var obj = document.getElementById("num"); var reg = new RegExp("^[0-9]*$"); if(!reg.test(obj.value)) alert("请输入数字!");}</script>

写法二：

<script type="text/javascript">function checknum(){var obj = document.getElementById("num");if(!/^[0-9]*$/.test(obj.value)) alert("请输入数字!");}</script>