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js tutorial--dom code to get elements

php是最好的语言Original: 2018-08-09 13:20:331389browse

Get elements:

document.getElementsByClassName ('class') Get elements by class name, as array of classes Form exists. getElementsByTagName
document.querySelector('selector') Gets the element through the CSS selector, the 1 that meets the matching conditions element.
document.querySelectorAll('selector') Gets elements through CSS selectors, in an array-like form.

## Class name operation:

Node.classList. add('class') Add class
Node.classList.remove('class') Remove class
Node.classList.toggle ('class') Switch the class, remove it if it exists, add it if it doesn't
Node.classList.contains('class') Check whether the class exists

Custom attributes:

In HTML5 we can customize attributes, the format is as follows data-* ="", for example: data-info="I am a custom attribute", through Node.dataset['info'] we can get the custom attribute value.

When we set the format as follows, we need to use camel case format to get it correctly: data-my-name="itcast", get Node.dataset['myName']

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .red{
            color: red;
        }
        .green{
            color: green;
        }
        .blue{
            color: blue;
        }
    </style>
</head>
<body>
<ul>
    <li>请选择</li>
    <li class="red">前端</li>
    <li class="green">java</li>
    <li class="blue">javascript</li>
    <li id="c">c++</li>
</ul>
<script>
    /*获取第一个li标签*/
    window.onload=function(){
        /*ElementsByTagName获取的是数组*/
        /*索引：不直观 以后的数据都是从后台动态获取，前台动态生成添加*/
        /*var cli=document.getElementsByTagName("li")[1];
        console.log(cli);*/

        /*query:查询  Selector：选择器   querySelector(传入选择器名称)*/
        /*querySelector:获取单个元素，如果获取的元素不止一个，那么只会返回满足条件的第一个元素*/
        /*参数要求：如果是类选择器，必须添加.  如果是id选择器， 必须添加# ,否则当成标签处理*/
        var javaLi=document.querySelector(".green");
        //var javaLi=document.querySelector("#c");
        console.log(javaLi);

        /*querySelectorAll获取满足条件的所有元素--数组*/
        var allLi=document.querySelectorAll("li")[0];
        console.log(allLi);
    }
</script>
</body>
</html>

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