The defer attribute is a boolean attribute. If the defer attribute is set, it specifies that the script is downloaded in parallel to parsing the page, and executed after the page has finished parsing.

Scripts with the defer attribute will execute in the order in which they appear in the document. This attribute allows the elimination of parser-blocking JavaScript where the browser would have to load and evaluate scripts before continuing to parse. async has a similar effect in this case.

Some browsers obey defer on <script> elements with inline code and without a src attribute, and some ignore it. Fortunately the spec does at least specify that async overrides defer. So you can treat all scripts as async and get a wide swath of browser support like so: <script defer async src="..."></script>

Luckily, there are two <script> attributes that solve the problem for us: defer and async. The defer attribute tells the browser not to wait for the script. Instead, the browser will continue to process the HTML, build DOM. The script loads “in the background”, and then runs when the DOM is …

Feb 27, 2024 · The "defer" attribute in <script> tags are used to specify that the script should be executed after the HTML document has been parsed. This attribute is primarily used to improve page loading performance by deferring the execution of non-essential scripts until after the document has been full

The defer attribute fetches the script parallel to HTML parsing but delays its execution until after HTML parsing is complete. This ensures that the script and DOM work as intended. In HTML, the `` tag is used to embed a JavaScript script in your webpage.

In this article, we will explore how deferring JavaScript can improve page load performance. We’ll look at why delaying script execution helps prevent render-blocking issues, how to determine which scripts to defer, and look at how deferring scripts can improve Core Web Vitals. Why defer JavaScript loading?

In XHTML, the defer attribute must be specified as <script defer=”defer”> as attribute minimization is forbidden. You can use this attribute on the <script> element. An external script can be executed in the following ways: When async is present, the script will be executed asynchronously while the page continues the parsing.

Use <script async> when the script does not rely on anything. when the script depends use <script defer>. Best solution would be add the <script> at the bottom of the body. There will be no issue with blocking or rendering.

Common uses for JavaScript are image manipulation, form validation, and dynamic changes of content. Tip: Also look at the <noscript> element for users that have disabled scripts in their browser, or have a browser that doesn't support client-side scripting. Tip: If you want to learn more about JavaScript, visit our JavaScript Tutorial.