Using Laravel Mix on Heroku

Setting up Laravel Mix on Heroku is very similar to how you'd set it up with Elixir. Because Laravel puts your front-end dependencies in devDependencies instead you just need to tweak the default configuration.

First, set YARN_PRODUCTION to false using the following command. This tells Heroku to install the devDependencies in your package.json, but leaves NODE_ENV as production.

$ heroku config:set YARN_PRODUCTION=false

Next, set the engines in your package.json. Make sure you have yarn at least 0.19.1 so that it respects the YARN_PRODUCTION environment variable.

Also add the postinstall key to scripts so that Heroku will compile your assets as you expect after everything has been installed.

{
  "engines": {
    "node": "7.6.0",
    "yarn": "0.21.3"
  },
  "scripts": {
    //
    "postinstall": "npm run production"
  },
  "devDependencies": {
    //
    "laravel-mix": "^0.8.1"
  }
}