<script type="text/javascript">
  /**
   *新增String物件的3個Method
  **/
  //去除前後(左右)空白
  String.prototype.Trim = function() {
   return this.replace(/(^[\s]*)|([\s]*$)/g, "");
  }
  //去左空白
  String.prototype.LTrim = function() {
   return this.replace(/(^[\s]*)/g, "");
  }
  //去除右空白
  String.prototype.RTrim = function() {
   return this.replace(/([\s]*$)/g, "");
  }
  function _Trim()
  {
   document.getElementById("ans").value = document.getElementById("str").value.Trim();
  }
  function _LTrim()
  {
   document.getElementById("ans").value = document.getElementById("str").value.LTrim();
  }
  function _RTrim()
  {
   document.getElementById("ans").value = document.getElementById("str").value.RTrim();
  }
 </script>
 
  
<div style="float: left;">
  <div>
    輸入要去空白字串
    <input id="str" type="text">
  </div>
<div>
    輸出除去結果字串
    <input id="ans" type="text">
  </div>
<div>
    <input onclick="_Trim(); return false;" type="button" value="去除左右空白">
    <input onclick="_LTrim(); return false;" type="button" value="去左邊空白">
    <input onclick="RTrim(); return false;" type="button" value="去右邊空白">
  </div>
</div>