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The wonderful use of jQuery's factory function $()

无忌哥哥Original: 2018-06-29 10:49:223513browse

The wonderful use of jQuery’s factory function $()

1. Understand the DOM structure: ancestor elements, parent elements, child elements, sibling elements, each element is a DOM object

2. You must first use the factory function $() to convert the DOM object into a jQuery object before you can use the method in jQuery

3.$ (selector): Pack/convert the DOM object obtained by selection into jquery object

4. The difference between jQuery object and DOM object:

4-1: jquery object is to package one or a group of DOM objects and process them uniformly. By default, it comes with a loop Iteration

4-2: The DOM object corresponds to one or more visual elements in the page, which provides raw materials for the jquery object

5. Conversion between DOM object and jquery object:

5-1: Convert DOM object to jquery object: $()

5-2: Convert jquery object to DOM object: get(index) or [index]

Note: $() is a DOM object packager. As long as you take it out one by one, it will be a DOM object

6.$() Summary: Convert DOM objects into jQuery objects so that you can use jQuery methods to process page elements uniformly and quickly.

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>jQuery的工厂函数$()的妙用</title>
</head>
<body>
<ul>
<li>我是列表项1</li>
<li>我是列表项2</li>
<li>我是列表项3</li>
<li>我是列表项4</li>
<li>我是列表项5</li>
</ul>
<script type="text/javascript" src="../js/jquery-3.3.1.js"></script>
<script type="text/javascript">
//任务:将第一个列表项背景换成天蓝色
//1.先用原生的js来实现:getElementsByTagName()是原生DOM对象上的方法
// document.getElementsByTagName(&#39;li&#39;)[0].style.backgroundColor = &#39;skyblue&#39;
//2.用jqery来实现 :css()是定义在jquery对象上的方法
// $(&#39;li:first-child&#39;).css(&#39;backgroundColor&#39;,&#39;skyblue&#39;)
//思考?能不能直接在jQuery对象上调用原生DOM对象的方法呢?答案是否定的
// $(&#39;li:first-child&#39;).style.backgroundColor = &#39;skyblue&#39;
//思考?能不能在原生DOM对象上面调用jquery中的方法呢?答案是否定的
// document.getElementsByTagName(&#39;li&#39;)[0].css(&#39;backgroundColor&#39;,&#39;skyblue&#39;)
//这是为什么呢?,因为这是二个不同的对象,下面我们进行测试
// document.write((document.getElementsByTagName(&#39;li&#39;)[0] === $(&#39;li:first-child&#39;)) ? &#39;我们完全一样&#39; : &#39;我们不一样&#39;)
//将jquery对象转为DOM对象,再调用原生对象方法
$(&#39;li&#39;)[0].style.backgroundColor = &#39;coral&#39;
$(&#39;li&#39;).get(2).style.backgroundColor = &#39;cyan&#39;
//将DOM对象转为jquery对象,就是使用工厂函数 $(),前面已说过,不更多言
</script>
</body>
</html>

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