What are the attributes of the JSscript tag

What are the attributes of the JS script tag:

• charset : Optional. Represents the character set of the code specified by the src attribute. This property is rarely used because most browsers ignore its value.
• defer : Optional. Indicates that script execution can be delayed until the document is fully parsed and displayed.
• language : Deprecated. Originally used to refer to the scripting language used to write code (such as JavaScript, JavaScript1.2 or VBScript ). Most browsers ignore this attribute, so there is no need to use it.
• src : Optional. Represents an external file containing code to be executed.
• type : Required. It can be seen as an alternative attribute of language, indicating the content type (also known as MIME type) of the scripting language used to write the code. Although text ext/javascript and text/ecmascript are no longer recommended, people still use text/javascript . In fact, the MIME type used by the server when sending JavaScript files is usually application/x-javascript , but setting this value in type may cause the script to be ignored. In addition, the following values ​​can be used in non-IE browsers: application/javascript and application/ecmascript . Taking into account convention and maximum browser compatibility, the current value of the type attribute is still text/javascript .

There are two ways to use the <script> element: embedding JavaScript code directly in the page and including external JavaScript files.

When using the script> element to embed JavaScript code, you only need to specify the type attribute for the script>. Then, just put the JavaScript code directly inside the element like this:

 scripttype="text/javascript">

  functionsayHi(){

  alert("Hi!");

  }

  /script>

The JavaScript code contained in the script> element will be interpreted from top to bottom. Take the previous example, the interpreter will interpret the definition of a function and then save the definition in its own environment. Until the interpreter has finished evaluating all the code inside script> element, the rest of the page will not be loaded or displayed by the browser.

When using script> to embed JavaScript code, remember not to include the string " /script>" anywhere in the code.

For example, a browser will generate an error when loading the following code:

  scripttype="text/javascript">

  functionsayScript(){

  alert('/script>');

  }

  /scrìpt>

Because according to the rules for parsing embedded code, when the browser encounters the string " /script> ", it will think that it is the closing /script> tag. This problem can be solved by splitting the string into two parts,

For example:

What are the attributes of the JSscript> tag:

 functionsayScript(){

  alert("/scr"+"ipt>");

  }

Writing it in two parts like this will not cause misunderstandings by the browser and thus will not cause errors.

If you are including an external JavaScript file via script> element, the src attribute is required. The value of this attribute is a link to an external JavaScript file.

For example:

  scripttype="text/javascript"src="example.js">/script>

In this example, the external file example.js will be loaded into the current page. The external file only needs to contain the JavaScript code that would normally be placed between the opening script> and the closing /script>. As with parsing embedded JavaScript code, page processing is temporarily stopped while an external JavaScript file is parsed (including downloading the file). If it is in an XHTML document, you can also omit the closing /script> tag in the previous example code.

For example:

  scripttype="text/javascript"src="example.js"/>

However, you cannot use this syntax in HTML documents. The reason is that this syntax does not conform to the HTML specification and cannot be correctly parsed by some browsers, especially IE.

By convention, external JavaScript files have a js extension. This extension is not required, however, as browsers do not check the extension of files containing JavaScript. This makes it possible to dynamically generate JavaScript code using JSP, PHP or other server-side languages.

It is important to note that a script> element with a src attribute should not contain additional JavaScript code between the script> and /script> tags.

In addition, you can include JavaScript files from external domains via the src attribute of the <script> element. This is what makes the script> element both powerful and controversial. In this respect, the script> element is very similar to the img> element, that is, its src attribute can point to a URL in a domain other than the domain of the current HTML page, for example:

  scripttype="text/javascript"src="http://www.somewhere.com/afile.js">/script>

This way, code located in external domains will be loaded and parsed just as if it were located in the page that loaded it. This allows you to serve JavaScript files from a different domain if necessary. However, you should be careful when accessing JavaScript files on a server that you do not control. If you are unlucky enough to encounter a malicious programmer, they may replace the code in this file at any time. Therefore, if you want to include code from a different domain, either you are the owner of that domain or the owner of that domain is trustworthy.

No matter how you include the code, the browser will parse them in the order in which the script> elements appear on the page. In other words, after the code contained in the first script> element is parsed, the code contained in the second script> will be parsed, and then the third and fourth.

This is the end of this article about the attributes of the JSscript tag. For more information about the attributes of the JSscript tag, please search for previous articles on 123WORDPRESS.COM or continue to browse the following related articles. I hope you will support 123WORDPRESS.COM in the future!