原型 - `Form.Element` 方法 clear()

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此方法将清理文本输入的内容。

语法

formElement.clear();

返回值

它返回一个 HTML 元素。

示例

此代码以一种方式设置文本字段，使其在第一次接收焦点时清理其内容。

<html>
   <head>
      <title>Prototype examples</title>
      <script type = "text/javascript" src = "/javascript/prototype.js"></script>
      
      <script>
         function showResult() {
            $('username').onfocus = function() {
               // if already cleared, do nothing
               if (this._cleared) return
	 
               // otherwise clear this
               this.clear()
               this._cleared = true
            }
         }
      </script>
   </head>

   <body onload = "showResult();">
      <p>Focus on username to see the result:</p>
      <br />
      
      <form id = "example" action = "#" onsubmit = "return false">
         <fieldset>
            <legend>User info</legend>
            <div>
               <label for = "username">Username:</label> 
               <input name = "username" id = "username" value = "Sai" type = "text">
            </div>
            <div>
               <label for = "age">Age:</label> 
               <input name = "age" id = "age" value = "23" size = "3" type = "text">
            </div>
            <div>
               <label for = "hobbies">Your hobbies :</label>
               <select name = "hobbies" id = "hobbies" multiple = "multiple">
                  <option>coding</option>
                  <option>swimming</option>
                  <option>hiking</option>
                  <option>drawing</option>
               </select>
            </div>
         </fieldset>
      </form>
      
   </body>
</html>

输出

prototype_form_management.htm
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