How to Make Your JavaScript Code 10x Faster (Proven Techniques 🚀)

The backbone of modern web applications is JavaScript, but sluggishness can hamper the complete user experience. Whether you build a complex web app from scratch or simply beef up the existing footprint, JavaScript performance enhancement is vital for better load times and efficiency.

We’re going to examine proven techniques in this guide to be able to speed up your JavaScript code up to 10 times faster, improving speed, responsiveness, and overall execution. Let’s dive in!

Optimize Loops and Reduce Computation

Use Efficient Looping Techniques

Optimize regular for-loops with some better alternatives.

❌ Slow Example:

for (let i = 0; i < arr.length; i++) {
  console.log(arr[i]);
}

✅ Faster Alternative:

for (const item of arr) {
  console.log(item);
}

🔹 Why? for...of is more optimized in modern JavaScript engines and reduces lookup time for arr.length.

🔹 Use .map(), .filter(), and .reduce() Instead of Loops

High-order functions allow better execution and are more easily readable.

✅ Optimized Example:

const squaredNumbers = numbers.map(num => num * num);

It transfers more quickly than for loops.

Minimize DOM Manipulations

The DOM (Document Object Model) is a slow one. Seeking too many excessive manipulations on DOM elements results in reflow and repaint which usually brings a slow JavaScript.

Batch Updates Instead of Individual Changes

❌ Slow Example:

document.getElementById("title").innerHTML = "New Title";
document.getElementById("content").innerHTML = "Updated Content";

✅ Optimized Approach:

const container = document.createDocumentFragment();
const title = document.createElement("h1");
title.textContent = "New Title";

const content = document.createElement("p");
content.textContent = "Updated Content";

container.appendChild(title);
container.appendChild(content);
document.body.appendChild(container);

Why? Using documentFragment reduces reflow/repaint cycles, boosting performance.

Use Debouncing & Throttling for Events

The scroll, resize and keypress JavaScript events, as often as hundreds of times each second, may grate against the inside of your application.

Debouncing (Limits Function Execution)

The function is executed after a certain delay once the user stops performing the action.

✅ Example:

function debounce(func, delay) {
  let timer;
  return function (...args) {
    clearTimeout(timer);
    timer = setTimeout(() => func.apply(this, args), delay);
  };
}

window.addEventListener("resize", debounce(() => {
  console.log("Window resized!");
}, 300));

Throttling (Limits Function Execution Rate)

It ensures that no function runs more than once every X milliseconds.

✅ Example:

function throttle(func, limit) {
  let lastFunc, lastTime;
  return function (...args) {
    const now = Date.now();
    if (!lastTime || now - lastTime >= limit) {
      func.apply(this, args);
      lastTime = now;
    }
  };
}

window.addEventListener("scroll", throttle(() => {
  console.log("User scrolling...");
}, 500));

Why? This significantly improves performance by reducing redundant function calls.

Use Asynchronous JavaScript (Async/Await & Promises)

Blocking operations slow the performance of JavaScript. Using async programming can perform better.

Avoid Blocking Code with Promise.all()

Instead of multiple requests being executed in a sequential manner, they can run parallely and return the desired information.

❌ Slow Example (Sequential Execution):

async function fetchData() {
  const user = await fetch("/api/user");
  const posts = await fetch("/api/posts");
  return { user, posts };
}

✅ Optimized Example (Parallel Execution):

async function fetchData() {
  const [user, posts] = await Promise.all([
    fetch("/api/user"),
    fetch("/api/posts"),
  ]);
  return { user, posts };
}

Why? Promise.all() executes both requests simultaneously, reducing wait time.

Minify and Compress JavaScript Files

Loads the page slowly. If they are very large, then the performance will be greatly impacted.

Minify JavaScript Using Tools Like:

✅ Terser – Reduces file size by removing whitespace, comments, and unused code.
✅ UglifyJS – Another excellent JavaScript minifier.

Enable Gzip or Brotli Compression

JavaScript file volume significantly decreases with the compression methodologies applied to the served files.

✅ Example (Enable Gzip in Nginx)

gzip on;
gzip_types text/javascript application/javascript;

Why? This reduces bandwidth usage and speeds up script loading.

Bonus Tip: Use a JavaScript Compiler Like SWC or Babel

Contemporary compilers like Babel and SWC (Speedy Web Compiler) would generate the JavaScript code, execute it, compile it, and store it directly in the memory for further optimizations.

In general, modern compilers such as SWC (Speedy Web Compiler) and Babel use JavaScript to increase program execution optimization.

✅ Example (Using SWC in a Webpack Project):

npm install @swc/core swc-loader --save-dev

Why? SWC compiles JavaScript 20x faster than Babel, making it ideal for high-performance apps.

Final Thoughts

By providing these techniques, JavaScript applications can run fast and give high speed performance which will be admired. 🚀

✅ Quick Recap:

✔ Optimize loops and computations
✔ Reduce DOM manipulations
✔ Use debouncing & throttling for events
✔ Implement asynchronous JavaScript effectively
✔ Minify & compress JavaScript files

These best practices would make your JavaScript code worth running 10 times faster without providing the user with frictions and enhance the performance of your site internally regarding Google Core Web Vitals.

let us know which optimization technique you are going to try first, In your comments section.