七个不允许错过的jQuery小技巧

六、计算子元素的个数

<div id="foo">
  <div id="bar"></div>
  <div id="baz">
    <div id="biz"></div>
    <span><span></span></span>
  </div>
</div>
<script src="http://apps.bdimg.com/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="text/javascript">
  //jQuery code to count child elements $("#foo > div").size()
alert($("#foo > div").size())
</script>

七、把元素定位到页面中间

<div id="foo" style="width:200px;height: 200px;background: #ccc;"></div>
<script src="http://apps.bdimg.com/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="text/javascript">
jQuery.fn.center = function() {
  this.css("position", "absolute");
  this.css("top", ($(window).height() - this.height()) / 2 + $(window).scrollTop() + "px");
  this.css("left", ($(window).width() - this.width()) / 2 + $(window).scrollLeft() + "px");
  return this;
}
//Use the above function as:
$('#foo').center();
</script>

读到这里的朋友就知道你没有错过学习的机会，把这些小技巧积累起来，一定会帮助大家设计出有创意和精美的Web页面。