JavaScript has become one of the most popular programming languages in the modern world. According to the surveys of W3Tech, 97.1% of developers use it on the client-side. The challenge of developing the client-side of the application is that the programmers can’t predict the technical characteristics of the clients’ devices. That means the web application must be perfectly optimized to fulfill the requirements of a picky customer.

We have made up a list of tips on how to optimize the JavaScript code, that can improve the performance.

 1. Say NO to the unused code

The bigger the code is, the more data should be passed to the client. Besides, the browser will need more time for code analysis and interpretation.

Sometimes you can enable features that are not used at all. It is better to store this code in the development environment and not to use it for production, so the client’s browser will not be burdened with extra code. Always ask yourself if the function or the part of the code is necessary.

You can remove unused code manually or with tools like Uglify or Google Closure Compiler. You can even use a technique called tree-shaking, which removes unused code from the application. Vendors like Webpack provide this technique. If you want to remove unused npm packages, you can use the npm prune command.

A handy solution is also to use a UI library with ready-made components and widgets. Such solutions can significantly speed up the development process and save money for the start-up.

 2. Always cache

The speed and performance of any website are increased with caching, as it reduces latency and network traffic. Therefore, the time required for the display is shortened. The tools such as Cache API or HTTP caching help to solve the issue. These caching mechanisms can process and restore the cache when posting new content.

3. Take out the garbage

JavaScript is a high-level language, thus it takes care of several low-level management systems, such as memory management. Garbage collection is a process common to most programming languages. It is the collection and release of memory that has been allocated to objects, but which is not currently used in any part of the program.

The process of garbage collection is done automatically in JavaScript. But unfortunately, not all cases run smoothly. In JavaScript ES6 Map and Set were presented with their weaker siblings, known as WeakMap and WeakSet. They allow you to collect unnecessary values and prevent memory leaks.

4. Don’t access the DOM

DOM access is slow. Altering the DOM makes things even slower, as it causes the whole redrawing of the layout.

Try to access DOM once and use it as a local variable. When it is no longer necessary, be sure to delete the value of the variable by setting it to null. This will prevent a memory leak, as it will allow the garbage collection process to run.

5. Shrink the files

Compression methods such as Gzip are really helpful. They can reduce the size of your documents by up to 80%. With the files compressed, the browser will need to load fewer resources. As a result, the performance of the site will improve significantly. So the smaller the files are, the better functional results you have.

6. Try UI libraries

We have saved the simplest tip for last. A wide choice of JS libraries provides developers with fully-fledged applications that can be used straight away. This approach allows programmers have extensive on-the-job training. Luckily most libraries support their users with tutorials and technical support, which shortens the learning curve even more.

Webix JS library is an example worth giving a try. First and foremost, it saves time for the development. The library contains 100+ widgets and controls, that can be easily integrated into any project. The code of the library is easily understandable, so you don’t need to bother about shortening the unused parts of the code. Besides, the library is light, fast, and customizable.

Tsyblienko Nataliya, marketing manager.