The wonderful use of jQuery's factory function $()
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('li')[0].style.backgroundColor = 'skyblue' //2.用jqery来实现 :css()是定义在jquery对象上的方法 // $('li:first-child').css('backgroundColor','skyblue') //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 // $('li:first-child').style.backgroundColor = 'skyblue' //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('li')[0].css('backgroundColor','skyblue') //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('li')[0] === $('li:first-child')) ? '我们完全一样' : '我们不一样') //将jquery对象转为DOM对象,再调用原生对象方法 $('li')[0].style.backgroundColor = 'coral' $('li').get(2).style.backgroundColor = 'cyan' //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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