[Defer] and [async] attributes of js, and jsdeferasync attributes

[Defer] and [async] attributes of js, and jsdeferasync attributes

[Defer]

You can add the defer attribute to <script> to tell the browser that this script does not need to be executed immediately. Then, the browser will execute this script after the file is fully loaded, which is equivalent to window. onload, but it is better than window. onload is more flexible.

Copy codeThe Code is as follows:
<Script defer = "true"> </script>

[Async]

Load JavaScript using the async attribute, so that the entire script can be asynchronously loaded and executed.

<Script> tag's defer Attribute-tells the browser that the script will not operate on DOM before the page is loaded, and the script will be downloaded in parallel with other resource files;
<Script> The async attribute of the tag-the new asynchronous and parallel modes of HTML5. The script will wait for the appropriate time to execute the code after the download is completed.

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