Optimizing Bundle Size and Speed with esbuild.do

In modern web development, speed is a feature. Slow build times frustrate developers and hinder productivity, while large, unoptimized bundles lead to slow-loading websites and a poor user experience. The build process itself has become a critical bottleneck. But what if you could compile, bundle, and minify your code in milliseconds, not minutes, and do it all through a simple API call?

Enter esbuild, an incredibly fast JavaScript bundler and minifier written in Go. Its performance is revolutionary. And now, with esbuild.do, you can harness this power programmatically as part of a seamless, API-driven workflow. Forget complex local setups and node_modules—it's time to embrace "Build as Code."

The Twin Challenges: Build Speed and Bundle Size

Before diving into the solution, let's appreciate the problem.

1. Developer Experience: Slow build times create a painful feedback loop. Every time you save a file, you wait. In a CI/CD pipeline, these delays compound, leading to slower deployments and longer queues for developers waiting to merge their code.
2. User Experience: The size of your JavaScript bundle directly impacts how quickly your page becomes interactive. Large bundles must be downloaded, parsed, and executed by the browser, all of which block the main thread and delay rendering. This can lead to higher bounce rates and lower conversion rates.

Optimizing both is not just a "nice-to-have"; it's essential for competitive applications.

How esbuild Changes the Game

esbuild was built from the ground up with a singular focus on speed. Unlike traditional bundlers written in JavaScript, esbuild is written in Go, a compiled language that runs on native code. It heavily leverages parallelism to utilize all available CPU cores, and its algorithms are designed for maximum efficiency.

The result? esbuild is often 10-100x faster than its counterparts. This isn't just an incremental improvement; it fundamentally changes what's possible with your build process.

The esbuild.do Advantage: Build as Code via API

While esbuild's CLI is fantastic for local development, modern infrastructure demands automation and integration. This is where esbuild.do shines. It exposes the full power of esbuild through a simple, robust API on the Agentic Workflow Platform.

Instead of running shell commands, you import and call an agent. This "Build as Code" approach offers significant advantages:

• Zero Dependencies: No need to install esbuild or manage package.json dependencies in your serverless functions or CI runners. Just make an API call.
• Programmatic Control: Define entry points and even entire virtual file systems in your code. Dynamically generate, transform, and bundle code on the fly.
• Ultimate Portability: Your build logic lives in your application code, making it testable, versionable, and executable anywhere—from a local script to a distributed cloud environment.

A Practical Example

Let's see just how simple it is. Imagine you want to bundle a TypeScript entrypoint that imports a utility function, then minify the output for production. With esbuild.do, your entire build step looks like this:

import { esbuild } from "jsr:@do/esbuild";

// Define your entrypoint code as a string
const entrypointCode = `
  import { add } from './math';
  console.log('Result:', add(2, 3));
`;

// Define a virtual file system for any other files
const otherFiles = {
  "./math.ts": "export const add = (a, b) => a + b;",
};

// Call the esbuild agent to bundle, transpile, and minify the code
const result = await esbuild.bundle({
  entrypoint: entrypointCode,
  files: otherFiles,
  options: {
    bundle: true,    // Follow imports and bundle them
    minify: true,    // Minify the output code
    platform: 'node', // Target the Node.js environment
    target: 'esnext',  // Use modern JavaScript syntax
  },
});

console.log(result.code);
// Expected output: "console.log(\"Result:\",5);"

In this example, we performed a complex build operation—transpiling TypeScript, resolving modules from a virtual file system, bundling them into a single file, and minifying the result—with a single, clean API call. The output is a tiny, optimized string ready for execution.

Frequently Asked Questions (FAQs)

What is esbuild.do?

esbuild.do is an agent on the .do platform that provides access to the esbuild JavaScript bundler as a simple API. It allows you to perform fast code bundling, minification, and transpilation without installing any local dependencies.

Why use esbuild through an API instead of the CLI?

Using esbuild via an API is ideal for programmatic workflows, CI/CD pipelines, and serverless environments. It allows you to integrate lightning-fast bundling directly into your applications and services, treating your build process as code.

What languages and formats does esbuild.do support?

Our esbuild agent supports a wide range of inputs including JavaScript (.js), TypeScript (.ts), JSX, and TSX. It can output modern JavaScript targeted for browsers or Node.js environments.

Start Building Faster Today

Slow builds and bloated bundles are a tax on productivity and performance. esbuild.do offers a powerful escape hatch. By providing the world's fastest bundler as-a-service, we empower you to create more efficient CI/CD pipelines, build dynamic serverless applications, and deliver faster experiences to your users.

Stop waiting for your tools. Integrate esbuild.do into your workflow and experience the future of JavaScript bundling.