js performance

How to Optimize JavaScript Performance

Jasmine Miah Developer Tips, Tricks & Resources

JavaScript is a common language in mobile and web app development.  Due to its popularity, JavaScript optimization is becoming increasingly necessary for improving application performance.  Let’s learn some of the challenges associated with JavaScript and how to optimize js performance.  


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Typical js performance challenges

There are a number of challenges that can impact JavaScript performance.  Here are common issues associated with js performance:

Poor quality event handling:

Proper use of Event Handlers can enhance JavaScript performance by decreasing the depth of the call stack. 

It is important to keep track of all Event Handlers so that the handlers do not perform without your knowledge. 

Unorganized code 

JavaScript is loose, which is both a pro and a con. 

The minute subset of lexical constructs allow developers to achieve a lot.  However, an absence of organization in the code can lead to insufficient resource allocation. 

This can hamper JavaScript performance to a large extent. Understanding ECMA is important for understanding JavaScript.  . 

Too many dependencies 

Sometimes, JavaScript dependencies are poorly managed or excessive. When this happens, the app’s performance will be negatively impacted. 

For example, mobile users with restricted bandwidth will need to wait longer for rendered objects. 

Inefficient iterations 

Iterations take a long time to process.  However, this is also beneficial.  The long processing time creates a perfect starting point for JavaScript optimization. As you fix irrelevant calls or loops in your code, your JavaScript performance will greatly improve.

Tips for js performance optimization

Trimming the HTML

JavaScript HTML is complex and plays a crucial role in querying time for querying and altering DOM objects. 

When you cut the app’s HTML in half, it is possible to double the DOM speed. This can be challenging, but it is possible by discarding the tags like <div> and <span>. 

Batching the DOM changes

Batch up DOM transformations to prevent recurring screen renderings. When creating style changes, make all the alterations at once instead of applying changes to each style individually. 

Learning the methods of asynchronous programming

JavaScript applications require many internal calls to numerous APIs for fetching data. 

Middleware is needed for every function because JavaScript is single-threaded. 

Synchronous components can sometimes lock up the full application. JavaScript manages asynchronous code using async.js. 

Async code does not block the thread.  Instead, the threat gets rammed to the event queue, which fires after the execution of other codes. 

With JavaScript async features, it is possible to unintentionally utilize an external library for reverting to asynchronous jamming calls. 

This can decrease JavaScript performance. Instead, employ asynchronous APIs in the code, especially in the crucial performance sections. 

Utilizing gzip compression

JavaScript files can be massive.  Utilize GZip to decompress and compress files. GZip decreases lag time, boosts application performance, and saves bandwidth.  With GZip, a server compresses a resource before sending it to the browser.   

Utilize HTTP/2

The latest edition of HTTP is HTTP/2 with improvements for boosting JavaScript performance and speeding up website performance. 

HTTP/2 utilizes multiplexing and enables sending  multiple responses and requests simultaneously. Buffering the DOM

If there are scrollable DIVs, it is possible to employ a buffer to get rid of DOM items that are not currently visible in the viewport. These techniques save both DOM traversal and memory usage.

Restrict library dependencies

Loading times can affect library dependencies so  it is important to keep the utilization to a minimum. 

The best way to get ride of external library dependencies is  to depend on in-browser technology. 

When using CSS selectors, utilize Sizzle.js instead of  jQuery. When libraries are comprising a single feature, it is vital to add CSS selectors separately. 

Keeping codes light and small

Keeping JavaScript code compact will decrease latency and improve performance.  When optimizing JavaScript performance, ask yourself: 

  • Is there a real requirement for this module?
  • What is the reason for utilizing this framework?
  • Is the overhead worth it?
  • Is there a simpler way of doing this?

Optimize JavaScript performance by converting  multiple JS files into one. 

Implementing Application Performance Management Tools for js Performance:

It is important to use an application performance management tool when it comes to optimizing JavaScript performance.  Application Performance Management tools like Retrace come with Real User Monitoring (RUM).  RUM accelerates web performances by allowing you to monitor front end and back end code together.  This more comprehensive perspective makes identifying bottlenecks easier and better pinpoints the correct solution. As website performance is optimized, web pages respond quicker and feel more interactive. End-users are happy, become more engaged, and ultimately, are more likely to buy.

RUM includes resource breakdowns. Resource breakdowns help you identify if images need to be optimized or stylesheets and scripts need to be minified or cached. RUM’s segmentation functionality allows for deeper insights. Use segmentation to monitor load times based on browser, geography, and device type. This makes it easy to identify opportunities to improve the overall experience by pinpointing optimal locations for CDNs.  Try your free, 14 day Retrace RUM trial today.