In modern web development, performance isn't a feature—it's a requirement. Users expect lightning-fast load times, and search engines reward it. A primary bottleneck for performance is often the size and complexity of JavaScript bundles. While the esbuild bundler is famous for its incredible build speed, it's also a formidable tool for creating highly optimized output files.
Enter esbuild.do, the service that puts the full power of esbuild behind a simple, scalable API. This post will guide you through concrete strategies for optimizing your bundle size and application speed using esbuild.do, transforming your build process into a finely-tuned, cloud-native workflow.
Every kilobyte counts. Large JavaScript files directly impact your site's Core Web Vitals:
By optimizing your bundles, you create a snappier user experience and improve your SEO. esbuild.do makes achieving these optimizations easier than ever, especially in CI/CD pipelines, serverless functions, or any agentic workflow where a local build toolchain is impractical.
At its core, esbuild.do lets you run esbuild tasks with a simple API call. You can define entry points, specify an output, and toggle powerful features on or off.
Here’s a baseline example using the @do-sdk/esbuild client to bundle and minify a TypeScript file:
import { Esbuild } from '@do-sdk/esbuild';
// Initialize the esbuild agent
const bundler = new Esbuild();
// Bundle and minify a TypeScript file via API
const { output } = await bundler.bundle({
entryPoints: ['src/app.ts'],
outfile: 'dist/bundle.js',
minify: true,
bundle: true,
platform: 'browser',
sourcemap: true
});
console.log(`Build complete: ${output.outfile}`);
This single API call transpiles TypeScript, bundles all dependencies into one file, and minifies the result. But this is just the beginning. Let's dive into more advanced optimization techniques.
Harness the full potential of our esbuild API to shrink your code and boost its performance.
Minification is the most fundamental optimization. While minify: true handles whitespace, comments, and semicolon removal, esbuild can go further by shortening variable and property names. This is enabled by default with the minify flag and is one of the most effective ways to reduce file size.
Tree shaking is the process of eliminating "dead code"—any functions, modules, or variables that you've imported but never actually used.
The good news? esbuild does this automatically whenever you use the bundle: true option. By analyzing your code's import and export statements, it intelligently includes only the code your application strictly needs. This "free" optimization is a major benefit of using a modern JavaScript bundler.
Why force a user to download code for a feature they might never use? Code splitting breaks your application into smaller, logical chunks that can be loaded on demand. This dramatically improves initial page load speed.
With esbuild.do, enabling code splitting is as simple as changing a few options. Instead of a single outfile, you specify an outdir and set splitting: true.
// API call for code splitting
const { output } = await bundler.bundle({
entryPoints: ['src/main.ts', 'src/admin.ts'],
outdir: 'dist/chunks',
splitting: true, // Enable code splitting
format: 'esm', // ES modules are required for splitting
bundle: true,
minify: true,
platform: 'browser'
});
console.log('Code splitting complete. Check the dist/chunks directory.');
In this example, esbuild will analyze the dependencies between main.ts and admin.ts. Any shared code will be extracted into a separate chunk, preventing duplication and ensuring the browser only downloads what's necessary for the initial view.
Transpiling modern JavaScript (ES2020+) down to an older standard like ES6 adds polyfills and boilerplate, increasing bundle size. If you know your audience uses modern browsers, you can tell esbuild to generate newer, more compact code with the target option.
// API call targeting modern browsers
const { output } = await bundler.bundle({
entryPoints: ['src/app.ts'],
outfile: 'dist/bundle.js',
target: 'es2022', // Target modern ECMAScript
bundle: true,
minify: true
});
By setting target: 'es2022', you tell the esbuild API to preserve modern syntax like optional chaining (?.) and nullish coalescing (??), which results in smaller and more efficient output for compatible browsers.
Imagine a serverless function that dynamically generates a custom analytics script for different clients. Installing a full Node.js toolchain in a serverless environment is slow and inefficient.
With esbuild.do, the workflow becomes trivial:
This entire process is fast, stateless, and infinitely scalable, perfectly demonstrating the power of a build tool API in modern cloud architecture.
Optimizing your web assets is no longer an optional step. With esbuild.do, you gain access to a state-of-the-art JavaScript bundler and TypeScript transpiler through a flexible API. You can move beyond slow, complex build setups and embrace a workflow that delivers both unparalleled build speed and meticulously optimized bundles.
By implementing minification, leveraging automatic tree shaking, and strategically using code splitting and modern targets, you can significantly reduce your bundle size, speed up your website, and simplify your development process.
Ready to supercharge your builds? Get started with esbuild.do today and experience the future of asset bundling.