Comment on the four asynchronous loading methods of js,

Last Update:2015-12-28 Source: Internet

Author: User

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Js asynchronous loading methods.

Solution 1:$ (Document). ready

<! DOCTYPE html>

Comments:

1. jquery needs to be referenced

2. compatible with all browsers.

Solution 2:<Script> tag async = "async" attribute

Definition and usage of async (HTML5 attributes)

The async attribute specifies that the script will be executed asynchronously once the script is available.

Example:

<script type="text/javascript" src="xxxxxxx.js" async="async"></script>

Comments:

1. New properties in HTML5 are supported by Chrome, FF, IE9 & IE9 + (IE6 ~ 8 is not supported ). In addition, this method cannot ensure that scripts are executed in sequence.

2. The async attribute is only applicable to external scripts (only when the src attribute is used ).

Solution 3:<Script> tag's defer = "defer" attribute

The defer attribute specifies whether the script execution is delayed until the page is loaded.

Some javascript scripts use the document. write method to create the current document content. Other scripts are not necessarily the same.

If your script does not change the content of the document, you can add the defer attribute to the <script> label to speed up document processing. Because the browser knows that it will be able to safely read the rest of the document without executing the script, it will postpone the interpretation of the script until the document has been displayed to the user.

Example:

<script type="text/javascript" defer="defer"> alert(document.getElementById("p1").firstChild.nodeValue); </script>

Comments:Compatible with all browsers. In addition, this method ensures that all scripts with the defer attribute are executed in order.

Solution 4:Dynamically create <script> tags

Example:

<!DOCTYPE html>

Comments:Compatible with all browsers.

The above is a distinction between the four asynchronous loading methods of js, hoping to help you learn about asynchronous loading of js.

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