How do I deploy my Typescript Node.js app to Heroku?

My problem was about missing Typescript npm modules. The Typescript compiler tsc was not found when deployed the app to Heroku.

The Heroku deploy process (rightly) does not install development dependencies, in my case the Typescript module was part of devDependencies and thus the tsc command was not running on the Heroku platform.

Solution 1

Add typescript to dependencies: npm i typescript -s

Solution 2

• Open Heroku console:

• Select console type:

• Run the command npm i typescript && npm run tsc

Fabian said that we could do something like:

"scripts": {
  "start": "node build/index.js",
  "build": "tsc",
  "postinstall": "npm run build"
}

As of me writing this, I tested this and can state: postinstall is not required since build script is ran by Heroku. If you want to do it without build script, then you can use heroku-postbuild which will run after dependencies are installed there you run tsc to compile.

Alternatively you can have the TypeScript compile as a postinstall hook and run node build/index.js as the only Procfile command:

Your package.json should contain a postinstall hint that gets executed after npm install and before the node process launches:

"scripts": {
  "start": "node build/index.js",
  "build": "tsc",
  "postinstall": "npm run build"
}

You can then leave your Procfile as is:

web: npm start

This 'build on deploy' approach is documented by Heroku here.

The command you've given Heroku is to launch the web "process" by compiling index.ts and dependencies and starting node at index.js. Depending on how things are timed, index.js might or might not exist at the time node starts.

You need to already have your sources compiled by the time you want to start your app. For example, web should just be web: node index.js or similar.

Each build process is different, so you need to figure that out for your own setup. But, suppose you have a classical setup where you push to git and then Heroku picks up that change and updates the app with the new slug. You could just compile things locally and include index.js and any other build output in the repository, for it to be available in the slug for Heroku to use.

A better approach is to use a build server which has an integration with Heroku. After you do the build there, configure it to send the build results to Heroku. Travis has a straighforward setup like this. This way you don't need to include build outputs in your repository, which is considered an anti-pattern.

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On a sidenode, try using a tsconfig.json to keep the tsc configuration. It will save you from having to write such long command lines all over the place.