esbuild-wasm

What is esbuild-wasm?

The esbuild-wasm package is a WebAssembly-based version of the esbuild bundler and minifier. It provides extremely fast build times and is designed to be used in environments where native binaries cannot be executed, such as in browsers or some serverless platforms. It supports transforming, bundling, and minifying JavaScript and TypeScript files.

What are esbuild-wasm's main functionalities?

Bundling JavaScript

This code initializes esbuild-wasm and bundles a JavaScript file, outputting a single bundled file. It demonstrates how to set up and execute a basic bundling process.

const esbuild = require('esbuild-wasm');
esbuild.initialize({ worker: true, wasmURL: '/path/to/esbuild.wasm' }).then(() => {
  esbuild.build({
    entryPoints: ['input.js'],
    bundle: true,
    outfile: 'output.js'
  }).catch(() => process.exit(1));
});

Minifying CSS

This example shows how to use esbuild-wasm to minify a CSS file. It sets up the esbuild environment and performs minification, outputting the minified CSS.

const esbuild = require('esbuild-wasm');
esbuild.initialize({ worker: true, wasmURL: '/path/to/esbuild.wasm' }).then(() => {
  esbuild.build({
    entryPoints: ['input.css'],
    minify: true,
    outfile: 'output.css'
  }).catch(() => process.exit(1));
});

Transpiling TypeScript

This code snippet demonstrates how to transpile TypeScript into JavaScript using esbuild-wasm. It includes setting up the environment, specifying the loader for TypeScript files, and bundling the output.

const esbuild = require('esbuild-wasm');
esbuild.initialize({ worker: true, wasmURL: '/path/to/esbuild.wasm' }).then(() => {
  esbuild.build({
    entryPoints: ['input.ts'],
    loader: { '.ts': 'ts' },
    outfile: 'output.js',
    bundle: true
  }).catch(() => process.exit(1));
});

Other packages similar to esbuild-wasm

webpack

Webpack is a popular JavaScript module bundler with a vast ecosystem of plugins. It offers more configuration options and plugins compared to esbuild-wasm but is generally slower in terms of build speed.

rollup

Rollup is another module bundler that focuses on producing efficient bundles. It is known for its tree-shaking capabilities, which are similar to esbuild-wasm, but Rollup typically has slower build times and less efficient minification.

parcel

Parcel is a web application bundler that requires zero configuration for quick setup. It provides fast build times similar to esbuild-wasm and supports various file types natively, but it might not reach the same speed for larger projects.

README

esbuild

This is the cross-platform WebAssembly binary for esbuild, a JavaScript bundler and minifier. See https://github.com/evanw/esbuild and the JavaScript API documentation for details.

Changelog

0.20.1

• Fix a bug with the CSS nesting transform (#3648)

  This release fixes a bug with the CSS nesting transform for older browsers where the generated CSS could be incorrect if a selector list contained a pseudo element followed by another selector. The bug was caused by incorrectly mutating the parent rule's selector list when filtering out pseudo elements for the child rules:

  /* Original code */
  .foo {
    &:after,
    & .bar {
      color: red;
    }
  }
  
  /* Old output (with --supported:nesting=false) */
  .foo .bar,
  .foo .bar {
    color: red;
  }
  
  /* New output (with --supported:nesting=false) */
  .foo:after,
  .foo .bar {
    color: red;
  }
  

• Constant folding for JavaScript inequality operators (#3645)

  This release introduces constant folding for the < > <= >= operators. The minifier will now replace these operators with true or false when both sides are compile-time numeric or string constants:

  // Original code
  console.log(1 < 2, '🍕' > '🧀')
  
  // Old output (with --minify)
  console.log(1<2,"🍕">"🧀");
  
  // New output (with --minify)
  console.log(!0,!1);
  

• Better handling of __proto__ edge cases (#3651)

  JavaScript object literal syntax contains a special case where a non-computed property with a key of __proto__ sets the prototype of the object. This does not apply to computed properties or to properties that use the shorthand property syntax introduced in ES6. Previously esbuild didn't correctly preserve the "sets the prototype" status of properties inside an object literal, meaning a property that sets the prototype could accidentally be transformed into one that doesn't and vice versa. This has now been fixed:

  // Original code
  function foo(__proto__) {
    return { __proto__: __proto__ } // Note: sets the prototype
  }
  function bar(__proto__, proto) {
    {
      let __proto__ = proto
      return { __proto__ } // Note: doesn't set the prototype
    }
  }
  
  // Old output
  function foo(__proto__) {
    return { __proto__ }; // Note: no longer sets the prototype (WRONG)
  }
  function bar(__proto__, proto) {
    {
      let __proto__2 = proto;
      return { __proto__: __proto__2 }; // Note: now sets the prototype (WRONG)
    }
  }
  
  // New output
  function foo(__proto__) {
    return { __proto__: __proto__ }; // Note: sets the prototype (correct)
  }
  function bar(__proto__, proto) {
    {
      let __proto__2 = proto;
      return { ["__proto__"]: __proto__2 }; // Note: doesn't set the prototype (correct)
    }
  }
  

• Fix cross-platform non-determinism with CSS color space transformations (#3650)

  The Go compiler takes advantage of "fused multiply and add" (FMA) instructions on certain processors which do the operation x*y + z without intermediate rounding. This causes esbuild's CSS color space math to differ on different processors (currently ppc64le and s390x), which breaks esbuild's guarantee of deterministic output. To avoid this, esbuild's color space math now inserts a float64() cast around every single math operation. This tells the Go compiler not to use the FMA optimization.

• Fix a crash when resolving a path from a directory that doesn't exist (#3634)

  This release fixes a regression where esbuild could crash when resolving an absolute path if the source directory for the path resolution operation doesn't exist. While this situation doesn't normally come up, it could come up when running esbuild concurrently with another operation that mutates the file system as esbuild is doing a build (such as using git to switch branches). The underlying problem was a regression that was introduced in version 0.18.0.