esbuild

What is esbuild?

esbuild is a fast JavaScript bundler and minifier. It compiles TypeScript and JavaScript into a single file, minifies it, and can also handle CSS and image assets. It's designed for speed and efficiency, utilizing parallelism and native Go code to achieve its performance.

What are esbuild's main functionalities?

Bundling JavaScript

This code bundles 'app.js' and its dependencies into a single file 'out.js'.

require('esbuild').build({
  entryPoints: ['app.js'],
  bundle: true,
  outfile: 'out.js'
}).catch(() => process.exit(1))

Minifying JavaScript

This code minifies 'app.js' to reduce file size and improve load times.

require('esbuild').build({
  entryPoints: ['app.js'],
  minify: true,
  outfile: 'out.js'
}).catch(() => process.exit(1))

Transpiling TypeScript

This code compiles a TypeScript file 'app.ts' into JavaScript and bundles it into 'out.js'.

require('esbuild').build({
  entryPoints: ['app.ts'],
  bundle: true,
  outfile: 'out.js'
}).catch(() => process.exit(1))

Serving files for development

This code starts a local server to serve files from the 'public' directory and bundles 'app.js' into 'public/out.js'.

require('esbuild').serve({
  servedir: 'public',
  port: 8000
}, {
  entryPoints: ['app.js'],
  bundle: true,
  outfile: 'public/out.js'
}).then(server => {
  // Server started
})

Other packages similar to esbuild

webpack

Webpack is a powerful and widely-used module bundler. It offers a rich plugin ecosystem and a highly configurable build process. Compared to esbuild, webpack is more mature with more features but is generally slower due to its JavaScript-based architecture.

rollup

Rollup is another JavaScript module bundler that focuses on producing efficient bundles for modern module formats like ES modules. It's known for its tree-shaking capabilities. Rollup is typically faster than webpack but slower than esbuild.

parcel

Parcel is a web application bundler that offers zero configuration out-of-the-box. It's faster than webpack and rollup but generally not as fast as esbuild. Parcel has a simpler user experience but may not be as flexible for complex configurations.

terser

Terser is a JavaScript parser, mangler, and compressor toolkit for ES6+. It's often used for minifying JavaScript code. While esbuild also minifies code, terser is a dedicated tool for this purpose and can be used alongside other bundlers.

README

esbuild

This is a JavaScript bundler and minifier. See https://github.com/evanw/esbuild and the JavaScript API documentation for details.

Changelog

0.21.5

• Fix Symbol.metadata on classes without a class decorator (#3781)

  This release fixes a bug with esbuild's support for the decorator metadata proposal. Previously esbuild only added the Symbol.metadata property to decorated classes if there was a decorator on the class element itself. However, the proposal says that the Symbol.metadata property should be present on all classes that have any decorators at all, not just those with a decorator on the class element itself.

• Allow unknown import attributes to be used with the copy loader (#3792)

  Import attributes (the with keyword on import statements) are allowed to alter how that path is loaded. For example, esbuild cannot assume that it knows how to load ./bagel.js as type bagel:

  // This is an error with "--bundle" without also using "--external:./bagel.js"
  import tasty from "./bagel.js" with { type: "bagel" }
  

  Because of that, bundling this code with esbuild is an error unless the file ./bagel.js is external to the bundle (such as with --bundle --external:./bagel.js).

  However, there is an additional case where it's ok for esbuild to allow this: if the file is loaded using the copy loader. That's because the copy loader behaves similarly to --external in that the file is left external to the bundle. The difference is that the copy loader copies the file into the output folder and rewrites the import path while --external doesn't. That means the following will now work with the copy loader (such as with --bundle --loader:.bagel=copy):

  // This is no longer an error with "--bundle" and "--loader:.bagel=copy"
  import tasty from "./tasty.bagel" with { type: "bagel" }
  

• Support import attributes with glob-style imports (#3797)

  This release adds support for import attributes (the with option) to glob-style imports (dynamic imports with certain string literal patterns as paths). These imports previously didn't support import attributes due to an oversight. So code like this will now work correctly:

  async function loadLocale(locale: string): Locale {
    const data = await import(`./locales/${locale}.data`, { with: { type: 'json' } })
    return unpackLocale(locale, data)
  }
  

  Previously this didn't work even though esbuild normally supports forcing the JSON loader using an import attribute. Attempting to do this used to result in the following error:

  ✘ [ERROR] No loader is configured for ".data" files: locales/en-US.data
  
      example.ts:2:28:
        2 │   const data = await import(`./locales/${locale}.data`, { with: { type: 'json' } })
          ╵                             ~~~~~~~~~~~~~~~~~~~~~~~~~~
  

  In addition, this change means plugins can now access the contents of with for glob-style imports.

• Support ${configDir} in tsconfig.json files (#3782)

  This adds support for a new feature from the upcoming TypeScript 5.5 release. The character sequence ${configDir} is now respected at the start of baseUrl and paths values, which are used by esbuild during bundling to correctly map import paths to file system paths. This feature lets base tsconfig.json files specified via extends refer to the directory of the top-level tsconfig.json file. Here is an example:

  {
    "compilerOptions": {
      "paths": {
        "js/*": ["${configDir}/dist/js/*"]
      }
    }
  }
  

  You can read more in TypeScript's blog post about their upcoming 5.5 release. Note that this feature does not make use of template literals (you need to use "${configDir}/dist/js/*" not `${configDir}/dist/js/*`). The syntax for tsconfig.json is still just JSON with comments, and JSON syntax does not allow template literals. This feature only recognizes ${configDir} in strings for certain path-like properties, and only at the beginning of the string.

• Fix internal error with --supported:object-accessors=false (#3794)

  This release fixes a regression in 0.21.0 where some code that was added to esbuild's internal runtime library of helper functions for JavaScript decorators fails to parse when you configure esbuild with --supported:object-accessors=false. The reason is that esbuild introduced code that does { get [name]() {} } which uses both the object-extensions feature for the [name] and the object-accessors feature for the get, but esbuild was incorrectly only checking for object-extensions and not for object-accessors. Additional tests have been added to avoid this type of issue in the future. A workaround for this issue in earlier releases is to also add --supported:object-extensions=false.