Where is the script tag usually written in HTML?

The position of the script tag: 1. Place it inside the head tag. The browser parses the HTML. When parsing the script tag, it will first download all the scripts and then parse other HTML; therefore, the content of the web page will be changed. Lagging presentation and poor user experience. 2. If placed inside the body tag, the browser will first parse the entire HTML page, and then download and parse the js. 3. After placing it after the body closing tag, the browser will ignore the previous "", so the actual effect is no different from writing it before the body closing tag.

The operating environment of this tutorial: Windows 7 system, HTML5 version, Dell G3 computer.

Generally, script tags will be placed at the head or tail. The head is in the head tag, and the tail is in the body, or it is placed after the body closing tag.

1. Put the script tag inside the head tag

    <title>获取DOM元素</title>
    <script>
        var myElement = document.getElementById("atag");
        console.log(myElement);
    </script>


    <div>
        <p>一个标签</p>
    </div>

Print result:

When the script tag is placed inside the head tag When the browser parses the HTML, when it parses the script tag, it will first download all the scripts, and then continue to parse other HTML. When the browser downloads js, multiple js cannot be downloaded at the same time, and when the browser downloads js, it will block the parsing of other HTML. Therefore, placing the script tag in the head will cause the web content to lag and lead to a poor user experience.

2. Place the script tag inside the body tag

    <div>
        <p>一个标签</p>
    </div>
<script>
    var myElement = document.getElementById("atag");
    console.log(myElement);
</script>

##Put the script tag at the end of the body, and the browser will parse it first Complete the entire HTML page, and then download the js. In this case, if there is an error in the js execution, at least the elements in the page can still be loaded, because the DOM document is executed in order from top to bottom. But for some web pages that are highly dependent on js, this will appear very slow.

3. The script tag is placed after the body closing tag.

    <div>
        <p>一个标签</p>
    </div>

<script>
    var myElement = document.getElementById("atag");
    console.log(myElement);
</script>

## Although the script tag is placed before and after the body closing tag, the printing results are It's the same, but starting from HTML 2.0, placing

after the

body closing tag is substandard. The reason why the browser will not report an error is because if appears after the body tag or the start tag of any element, it will be a prase error (syntax error) and the browser will ignore it. The previous

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