esbuild-copy-static-files

An esbuild plugin to efficiently copy static files from a source directory to a destination directory.

✔️ Only copy files that changed (it compares an MD5 hash of each file)
✔️ No 3rd party dependencies (it only uses a few functions from the Node standard library)

Why?

I mainly created this because a certain live reloading tool I use didn't filter out files that didn't change. This resulted in dozens of unnecessary file being copied and log output in development every time I changed a single CSS or JS file. It was wildly inefficient.

This plugin fixes the above because it'll only copy static files if they changed on disk since they were last copied.

How it works at a high level

For most web apps, when it comes to my front-end I like the idea of this type of directory structure:

# This is where your assets are located and is used as input for esbuild.
assets/
├── css/
│   └── app.css
├── js/
│   └── app.js
├── static/
│   ├── images/
│   │   └── logo.png
│   ├── favicon.ico
│   ├── robots.txt
├── esbuild.config.js
├── package.json
├── postcss.config.js
├── tailwind.config.js
└── yarn.lock

# This is the output of where esbuild will write its file(s) to.
public/
├── css/
│   └── app.css
├── js/
│   └── app.js
├── images/
│   └── logo.png
├── favicon.ico
├── robots.txt

In my opinion it's really nice having all of your assets in 1 spot which then get output to another location.

esbuild manages the js/ directory and TailwindCSS (or whatever you prefer) manages the css/ directory but that leaves us with a bunch of static files that are composed of HTML, icons, images, fonts and more.

This esbuild plugin will copy your static files to your esbuild output directory. No processing will be done on these static files. It's a quick cp and only files that have changed are copied so it's really efficient.

You can name your static/ and public/ directories and configure their paths however you want. We'll go over all of the configuration options in a bit.

Installation

# Prefer Yarn?
yarn add --dev esbuild-copy-static-files

# Or NPM instead?
npm install --save-dev esbuild-copy-static-files

Getting Started

If you had the same directory structure as above, here's the bare minimum esbuild config to get going:

const esbuild = require('esbuild')
const copyStaticFiles = require('esbuild-copy-static-files')

esbuild.build({
  entryPoints: ['./js/app.js'],
  outfile: '../public/js/app.js',
  bundle: true,
  minify: true,
  sourcemap: false,
  watch: false,
  plugins: [copyStaticFiles()],
})

Configuration

This plugin uses Node's fs.cpSync function under the hood. Any option that it has can be configured here.

Here's a list of what you can configure and the default values if you don't override them:

  plugins: [
    copyStaticFiles({
      src: './static',
      dest: '../public',
      dereference: true,
      errorOnExist: false,
      filter: EXPLAINED_IN_MORE_DETAIL_BELOW,
      preserveTimestamps: true,
      recursive: true,
    })
  ],

In most cases you'll likely only change the src and dest to fit your project's directory structure.

Here's the docs of every configurable option from Node's documentation:

• src source path to copy.
• dest destination path to copy to.
• dereference dereference symlinks.
• errorOnExist when force is false and the destination exists, throw an error.
• filter function to filter copied files / directories. Return true to copy the item, false to ignore it.
• force overwrite existing file or directory. The copy operation will ignore errors if you set this to false and the destination exists. Use the errorOnExist option to change this behavior.
• preserveTimestamps when true timestamps from src will be preserved.
• recursive copy directories recursively.

How does the filter function work?

By default it will filter out, AKA skip copying any files that haven't changed. It does this by getting the MD5 hash of each src and dest file. If both files have the same MD5 hash then it get skipped.

This is nice because if you had let's say 50 static files and only 1 of them changed then only 1 file will get copied.

Using a custom filter function

If you can think of a more efficient way of detecting which file(s) should get copied you can customize the filter function by providing your own function that returns true or false based on whatever criteria you prefer.

Here's an example of a simple filter function that always returns true:

  plugins: [
    copyStaticFiles({
      filter: function () { return true },
    })
  ],

About the author

• Nick Janetakis | https://nickjanetakis.com | @nickjanetakis

I'm a self taught developer and have been freelancing for the last ~20 years. You can read about everything I've learned along the way on my site at https://nickjanetakis.com.

There's hundreds of blog posts / videos and a couple of video courses on web development and deployment topics. I also have a podcast where I talk with folks about running web apps in production.