Javascript Can You Defer Inline

Here’s an example HTML code for the subheading “What is Inline Scripting in JavaScript?” in a blog post titled “JavaScript: Can You Defer Inline?”:


What is Inline Scripting in JavaScript?

Inline scripting in JavaScript is the practice of embedding JavaScript code directly into an HTML document, typically within the <script> tag in the <head> or <body> section. This code is executed immediately as soon as the corresponding HTML element is encountered during the parsing of the document.

While inline scripting can be convenient, it can also lead to several performance issues, including slower page loading times and decreased search engine optimization (SEO) rankings. Therefore, it’s generally considered best practice to externalize JavaScript code into separate files or defer its execution to after the page has loaded using the defer or async attributes.


Note: This example code emphasizes the importance of avoiding inline scripting and using alternative methods for better performance and SEO.

How Defer Attribute Works in JavaScript

The defer attribute is used in JavaScript to indicate that the script should be executed after the page has finished loading. This means that the script will not block the loading of other elements on the page, such as images or other scripts.

When a script is included with the defer attribute, it will be downloaded in the background while the page continues to load. Once the page has finished loading, the script will then be executed in the order that it appears in the HTML document.

It is important to note that the defer attribute only works for external scripts, and not for inline scripts. This means that any JavaScript code that is included directly in the HTML document will still block the loading of other elements on the page, even if it has the defer attribute.

Overall, using the defer attribute in JavaScript can help to improve the performance and loading times of web pages, ensuring that users have a better experience when browsing the site.

The Pros and Cons of Using Defer Attribute in JavaScript

JavaScript is a popular programming language that is used to add interactivity to web pages. There are several ways to include JavaScript in a web page, and one of them is by using the defer attribute. The defer attribute is used to tell the browser to defer the execution of the JavaScript code until the entire HTML document has been parsed. This can have some benefits, but it also has some drawbacks.


  • Improved Page Load Time: Using the defer attribute can improve the page load time of your web page because the browser can download and parse the HTML document without having to wait for the JavaScript code to execute.
  • Better User Experience: With faster page load times, users can access your web page more quickly and have a better user experience. They won’t have to wait as long for the page to load, which can reduce bounce rates and increase engagement.
  • Reduced Blocking: JavaScript code can block the rendering of the page, which can cause delays and slower page load times. By using the defer attribute, the JavaScript code is downloaded in the background and executed after the HTML document has been parsed, reducing blocking and improving the user experience.


  • Limited Browser Support: Not all browsers support the defer attribute, which means that if your web page relies heavily on JavaScript code, it may not work as expected on older browsers.
  • Execution Order: If your web page has multiple JavaScript files with the defer attribute, they will execute in the order in which they are specified in the HTML document. This could cause issues if your code relies on a specific order of execution.
  • Delay in JavaScript Execution: If your web page requires immediate execution of JavaScript code, using the defer attribute may not be the best approach. The delay in execution could cause issues with functionality and interactivity.

Overall, using the defer attribute in JavaScript has its pros and cons. It can improve page load times and provide a better user experience, but it also has limitations and may not be suitable for all web pages. It’s important to carefully consider the needs of your web page and the audience you’re targeting before deciding whether or not to use the defer attribute.

How to Defer Inline Scripting in JavaScript

When it comes to improving website performance and speed, one technique that can be useful is deferring inline scripting. Inline scripting refers to code that is included directly in the HTML document, rather than in an external file. While this can be convenient for small snippets of code, it can slow down the loading of the webpage, as it prevents the HTML file from being parsed and the DOM from being constructed until the JavaScript code has completely loaded and executed. Here’s how to defer inline scripting:

  1. Move the JavaScript code to an external .js file. This allows the HTML file to be parsed and the DOM to be constructed before any JavaScript code is loaded or executed.
  2. Add defer attribute to the script tag that links to the external .js file. This tells the browser to download the script asynchronously while the HTML file is loading, but to defer its execution until the HTML file has been completely parsed.
  3. Alternatively, you can also use the async attribute instead of the defer attribute. This will download and execute the script as soon as it becomes available, but without blocking the parsing of the rest of the HTML file. However, keep in mind that this may cause the JavaScript code to execute out of order, so it’s important to use it only for scripts that don’t rely on any other scripts or dependencies.

By deferring inline scripting in JavaScript, you can improve the performance and speed of your website, resulting in a better user experience for your visitors.

Sure, here’s an example of the HTML code you can use for the subheading “Understanding Browser Rendering with Defer Attribute”:


Understanding Browser Rendering with Defer Attribute


In summary, the `defer` attribute in JavaScript helps with the rendering of web pages by allowing scripts to be parsed in the background while the page is loading. This can help improve the overall performance and speed of a website for the end user. However, it’s important to note that the `defer` attribute should not be used with inline JavaScript, as this can cause issues with the rendering and processing of the page.

If you’re using external JavaScript files, it’s a good idea to add the `defer` attribute to the `script` tag for these files to help optimize your website’s performance.

Common Inline Scripting Mistakes to Avoid in JavaScript

Inline scripting in JavaScript can be handy at times, but it can also lead to some common mistakes that should be avoided. Here are some mistakes to look out for:

  • Not using variables: One common mistake is not using variables when writing inline scripts. This can lead to code that is difficult to read and understand, and it can also make debugging more difficult.
  • Not using proper syntax: Another mistake is not using proper syntax. JavaScript has a strict syntax, and if you don’t follow it, your code may not work as expected.
  • Not testing your code: It’s important to test your code before deploying it, especially when using inline scripting. This can help you catch any errors or bugs before they cause problems for your users.
  • Not using asynchronous loading: If you’re using inline scripting, it’s important to use asynchronous loading to avoid slowing down your page. You can use the “defer” or “async” attributes to achieve this.
  • Not using a separate file: Finally, it’s generally a good idea to use a separate file for your JavaScript code instead of using inline scripting. This can make your code easier to manage and maintain, and it can also improve performance.

By avoiding these common mistakes, you can ensure that your inline JavaScript code is efficient, effective, and bug-free.

Best Practices for Using Defer Attribute in JavaScript

If you’re working with JavaScript, you are probably familiar with the defer attribute. It allows you to defer the execution of the script until the entire page is loaded. This can provide a significant boost to the performance of your website, especially if you have large scripts or slow-loading resources. However, there are some best practices you should follow to ensure you’re using the defer attribute correctly.

  • Always include the defer attribute within the script tag.
  • Don’t use defer for scripts that need to run before the page is fully loaded. For example, if you need to load a script that provides critical functionality to the page, you should place it before the closing body tag.
  • Don’t use defer for small scripts that load quickly. In these cases, the overhead required to defer the script may actually slow down your page’s performance.
  • Avoid using defer when loading third-party scripts or resources. They may not be designed to work with the defer attribute and this can cause problems with the overall functionality of your page.

By following these best practices, you can ensure that you’re using the defer attribute effectively and optimizing the performance of your website.

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