Prototype - previous() 方法

如果指定了与 cssRule 匹配的 index，则此方法返回元素的上一个同级元素或第 index 个元素。如果未提供 cssRule，则考虑所有先前的同级元素。如果没有先前的同级元素符合这些条件，则返回 undefined。

语法

element.previous([cssRule][, index = 0] );

返回值

返回 HTML 元素。如果没有先前的同级元素符合这些条件，则返回 undefined。

示例

<html>
   <head>
      <title>Prototype examples</title>
      <script type = "text/javascript" src = "/javascript/prototype.js"></script>
      
      <script>
         function showResult() {
            var str = $('saying').previous();
            alert( "$('saying').previous() " + str.innerHTML );

            var str = $('saying').previous(0);
            alert( "$('saying').previous(0) " + str.innerHTML  );
   
            var str = $('saying').previous('h3');
            alert( "$('$('saying').previous('h3') " + str.innerHTML  );

            var str = $('ida-red').previous( '.yummy');
            alert( "$('ida-red').previous( .yummy ) " + str.innerHTML );

            var str = $('ida-red').previous( 5 );
            alert( "$('ida-red').previous() " + str );
         }
      </script>
   </head>

   <body>
      <p>单击按钮查看结果。</p>
      
      <ul id = "fruits">
         <li id = "apples">
            <h3 id = "title">Apples</h3>
            <ul id = "list-of-apples">
               <li id = "golden-delicious">Golden Delicious</li>
               <li id = "mutsu">Mutsu</li>
               <li id = "mcintosh" class = "yummy">McIntosh</li>
               <li id = "ida-red" class = "yummy">Ida Red</li>
            </ul>
            <p id = "saying">An apple a day keeps the doctor away.</p>  
         </li>
      </ul>
      <br />
      
      <input type = "button" value = "Show Result" onclick = "showResult();"/>
   </body>
</html>

输出

prototype_element_object.html