返回值:jQueryprevAll([selector])

Get all preceding siblings of each element in the set of matched elements, optionally filtered by a selector.

Given a jQuery object that represents a set of DOM elements, the .prevAll() method allows us to search through the predecessors of these elements in the DOM tree and construct a new jQuery object from the matching elements.

The method optionally accepts a selector expression of the same type that we can pass to the $() function. If the selector is supplied, the elements will be filtered by testing whether they match it.

Consider a page with a simple list on it:

<ul>
   <li>list item 1</li>
   <li>list item 2</li>
   <li class="third-item">list item 3</li>
   <li>list item 4</li>
   <li>list item 5</li>
</ul>

If we begin at the third item, we can find the elements which come before it:

$('li.third-item').prevAll().css('background-color', 'red');

The result of this call is a red background behind items 1 and 2. Since we do not supply a selector expression, these preceding elements are unequivocally included as part of the object. If we had supplied one, the elements would be tested for a match before they were included.

示例:

Locate all the divs preceding the last div and give them a class.

<!DOCTYPE html>
<html>
<head>
<style>

  div { width:70px; height:70px; background:#abc; 
        border:2px solid black; margin:10px; float:left; }
  div.before { border-color: red; }
  </style>
<script src="jquery.min.js"></script>
</head>
<body>

<div></div>
  <div></div>
  <div></div>
  <div></div>

<script>

$("div:last").prevAll().addClass("before");

</script>
</body>
</html>
演示: