JavaScript is the foundation of modern web programming, supporting everything from dynamic websites to interactive applications. However, as your projects become more complicated, it becomes increasingly important to guarantee that your JavaScript code remains performance-optimized. A script that is not properly optimised can result in slow load times, laggy interfaces, and a bad user experience. But do not worry! With the correct approaches and best practices, you can turbocharge your JavaScript code.
In this post, we’ll look at ten crucial JavaScript tips and tricks for improving performance and ensuring your code works smoothly and quickly.
1. Minimise DOM Access
The text Object Model (DOM) is an important component of any web page, representing the structure of the HTML text. However, one of the most performance-intensive processes in JavaScript is accessing and manipulating the DOM. To optimise the code:
Cache the DOM elements: Instead of constantly searching the DOM for the same element, put it in a variable. This reduces the number of times your code must contact the DOM.
Copy the JavaScript code.
const button = document.getElementById(‘submit-button’);
button.addEventListener(‘click’, () => {
// Do something
});
- Batch DOM Updates: If you need to make multiple changes to the DOM, do them all at once. This minimises the number of reflows and repaints, which are expensive operations in terms of performance.
Also Read – 11 Useful Attributes of HTML You Must Know
2. Use Event Delegation
Handling events efficiently can significantly enhance your website’s performance, particularly when working with a high number of items. Event delegation is a strategy that involves assigning a single event listener to a parent element rather than numerous listeners to each child element. This decreases memory utilisation and the amount of event handlers that must be executed.
javascript
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document.querySelector(‘#parent’).addEventListener(‘click’, (event) => {
if (event.target.matches(‘.child-element’)) {
// Handle the click event
}
});
3. Opt for Native Methods Over Libraries
While libraries like jQuery and Lodash are popular because to their ease of use, they may introduce unnecessary overhead in your code. Modern browsers have a plethora of native techniques that are as strong, if not more so. For instance, instead of using jQuery’s .each() function, you can use the native forEach() method:
javascript
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const elements = document.querySelectorAll(‘.items’);
elements.forEach((item) => {
// Process item
});
This not only reduces your dependency on external libraries but also leads to leaner, faster code.
4. Defer and Async Script Loading
If JavaScript files are not loaded efficiently, they can cause a web page to fail to render. By default, scripts are loaded synchronously, which can cause page content to appear later. To avoid this, utilise the defer and async properties to load your scripts.
- Defer: The script is loaded in the background and run once the HTML parsing is completed.
- Async: The script is loaded and performed asynchronously, so it does not impede page rendering.
html
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<script src=”script.js” defer></script>
<script src=”analytics.js” async></script>
Using these attributes appropriately can significantly reduce load times, improving the user experience.
5. Reduce Function Call Overheads
Every time a function is called in JavaScript, there is some cost associated. To minimise this:
Inline Small Functions: Inlining tiny, frequently used functions can help reduce the overhead associated with function calls.
javascript
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// Instead of
function double(x) {return x * 2;}
const result = double(5);
// Use
const result = 5 * 2;
- Avoid Deep Recursion: Recursive functions can cause performance concerns, especially on large datasets. Wherever possible, employ iteration rather than recursion.
6. Optimise Loops
Loops are an essential component of JavaScript, but they can be a performance bottleneck if not used properly. Here are a few tips:
Cache Loop Length: Avoid recalculating an array or collection’s length on each iteration of a for-loop.
javascript
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const items = document.querySelectorAll(‘.item’);
for (let i = 0, len = items.length; i < len; i++) {
// Do something with items[i]
}
- Use forEach and map: These methods are often more efficient and easier to read than traditional for-loops.
7. Implement Lazy Loading
Lazy loading is a strategy in which specific resources, such as graphics or scripts, are loaded only when required. This can drastically reduce the initial load time of a page, particularly on media-rich websites.
- Images: Use the loading=”lazy” attribute in your <img> tags to defer the loading of off-screen images.
- Scripts: Dynamically load scripts only when they are required, using techniques such as import().
javascript
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if (userHasClicked) {
import(‘./heavy-script.js’)
.then(module => {
module.someFunction();
});
}
8. Use Web Workers for Heavy Computation
Because JavaScript is single-threaded, intensive computation can cause the UI to become slow, resulting in a poor user experience. Web Workers allow you to run scripts in background threads, freeing up the main thread so that the UI remains responsive.
javascript
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const worker = new Worker(‘worker.js’);
worker.postMessage(data);
worker.onmessage = function(e) {
console.log(‘Worker said: ‘, e.data);
};
This is particularly useful for tasks like image processing, complex calculations, or working with large data sets.
9. Use Throttling and Debouncing
When dealing with events that occur frequently, such as scrolling or resizing, it is critical to manage how frequently your code executes. Throttling and debouncing are methods for limiting the number of times a function is executed.
- Throttling: Limits the number of times a function can be called during a given period.
- Debouncing: Delays the execution of a function until a defined time has passed since the last time it was called.
javascript
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function throttle(fn, limit) {
let lastCall = 0;
return function(…args) {
const now = (new Date()).getTime();
if (now – lastCall >= limit) {
lastCall = now;
return fn(…args);
}
};
}
window.addEventListener(‘resize’, throttle(() => {
console.log(‘Resized!’);
}, 1000));
10. Compress and Minify Your JavaScript Files
One of the simplest ways to increase the efficiency of your JavaScript code is to reduce the size of the files. Smaller files load faster, which is important for performance, particularly on slower networks.
- Minify: Minification is the process of deleting extraneous characters from your code, such as whitespace, comments, and line breaks, without impacting its functionality. This procedure can be automated using tools such as UglifyJS, Terser, and Google Closure Compiler.
- Compression: After minification, you can minimise file size by compressing JavaScript scripts using Gzip or Brotli. Most modern web servers allow on-the-fly compression, sending the compressed version to the browser, which decompresses it on the client side.
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# Example command to minify and compress a file
uglifyjs input.js -c -m -o output.min.js
gzip output.min.js
By compressing and minifying your JavaScript files, you allow users to download and execute your scripts as rapidly as possible, resulting in shorter load times and a better overall user experience.
Conclusion
Applying these ten JavaScript tips and hacks can greatly improve the performance of your web applications. Whether you’re decreasing DOM access, utilising event delegation, or effectively applying script loading strategies, each suggestion helps to create a faster, more responsive user experience. Remember that successful JavaScript speed optimisation entails understanding how your code interacts with the browser and making that interaction as efficient as feasible. Happy coding!
