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7 Tips to Improve JavaScript Performance

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  • Last Updated : 15 Apr, 2021

When you’re building a website the most important thing that matters a lot for the users is the performance of the website. It is very frustrating for the users when they have to wait for a long time for a webpage to reload.  A lot of websites are built on JavaScript and accelerating the performance of these websites is not easy. 


Optimizing the website plays a major role in accelerating the performance of a web application. You can also automate few tasks and use various technologies to speed up the performance of the application. In a survey, it was found that 47% of visitors expect a website to load in less than 2 seconds and 40% of visitors leave the website if the loading takes more than 3 seconds. 

In this blog, we are going to discuss some effective ways that will improve your web application performance. 

1. Reduce Application Size With Webpack

The size of the application gets increased when you keep adding JavaScript modules in the application. This method increases more files in your application, and thus the application becomes slower and bulkier. This decreases the overall quality of the application. Adding larger file size creates a massive gap between the content developers wrote and what the browser could understand. 

To resolve this issue coders started using helper code polyfills that ensured that the browser understood the code correctly. 

A static module bundler webpack is also being used to resolve this issue. Webpack creates the dependency graph using the existing module. Webpack explores the packages and creates a new package with a minimum number of files that are required to run the application. 

2. Use Cache in The Browser

There are two methods to use cache in the browser by which you can increase the performance of the website. You can use the JavaScript Cache API or you can use the HTTP protocol cache. You need to install a service worker for JavaScript Cache API. 

The reason behind using a cache is the repeated use of scripts to access a specific object in your application. Performance immediately gets increased when you store the repeated object inside a user-defined variable as well as a subsequent reference to that object. 

3. Remove Unused JavaScript

Remove the JavaScript file which is of no use in your application. It will reduce the transmission time, and it will also reduce the time which it takes for the browser to analyze and compile the code. Remove all the functionalities from your application which of no use for the users. Remove that with all the JavaScript code associated with it. 

Your web application will load faster and the user will have a better experience. Remove the unnecessary libraries or dependencies from your code that don’t serve any purpose.

4. Place JavaScript at The Bottom of the Page

This is one of the common techniques developers prefer to speed up the performance of the website. Placing JavaScript code at the top of the webpage slower down the performance. It’s good to place it at the bottom. Your webpage won’t just load faster but also in some cases it saves the total amount of code needed

5. Use Minification

This is another common technique to follow in web development when it comes to loading faster a website. You can reduce the size of your file by removing the unwanted JavaScript documents character such as tabs, spaces, etc. When you’re doing it make sure that you’re not changing the functionality of the website. 

A lot of minification tools are available to minify your file or to unminify your file. Doing this will load your web application faster and users will have a better experience.

6. Use Gzip Compression

JavaScript files can be very large that may impact the load time of your website. Gzip which is good software can be used to compress your JavaScript file. Today most of the servers and clients support Gzip. 

When a browser requests a resource, the server compresses the response before sending it to the web browser. This software reduces the size of the JavaScript file, saves bandwidth, and accelerates the performance of the website. 

7. Avoid Unnecessary Access to DOM

Accessing DOM slower down the performance of the website. The browser has to refresh the page every time when you interact with the DOM outside the JavaScript native environment. It’s good to keep DOM access to a minimum or in your web application if you need to read the content several times then it’s good to save it in local variables. 

Keep in mind that if you remove the value of the DOM then set the variable to NULL to avoid the memory leak in your application. 


These were some useful techniques to boost the performance of the website. Although these are good techniques still you should follow some best practices to boost the performance. Avoid unnecessary nested loops and recursive calls. Use search array instead of using a switch case statement. Use bit-level operators in your code to take the advantage of fewer processor cycles. Also, avoid using global variables and consuming too much memory. 

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