Node.js Cloud Native Buildpack Builds
Last updated December 04, 2024
Table of Contents
Heroku’s Node.js buildpacks have different build behavior depending on whether an app uses classic or Cloud Native Buildpacks (CNB).
This article describes the build behavior for apps using Heroku’s Node.js Cloud Native Buildpack and how to customize the build process. Node.js applications follow the same build process when using npm, pnpm, or Yarn package managers.
This article is only applicable to apps use the Cloud Native Buildpack. For classic Node.js apps, see Node.js Classic Buildpack Behavior.
Package Installation
By default, Heroku installs all dependencies listed in package.json under dependencies and devDependencies.
Heroku uses the lockfiles (package-lock.json, pnpm-lock.yaml, or yarn.lock) to install the expected dependency tree. Check those files into Git to ensure the same dependency versions across environments. If you use npm, Heroku uses npm ci to set up the build environment.
Build Failures
If a build fails, the Node.js buildpack identifies common issues in Node applications and provides warnings with best practice recommendations.
Environment Variables
Your app’s config vars are available during the build, so you can adjust build behavior based on the values of environment variables. For example:
$ heroku config:set MY_CUSTOM_VALUE=foobar
Customizing the Build Process for Cloud Native Buildpack Apps
To allow for customization of the build process for your CNB application, the following scripts get executed by the chosen package manager in the order listed if they are defined in package.json:
heroku-prebuildheroku-buildorbuildheroku-postbuild
If heroku-build and build are present, only heroku-build executes.
These scripts run after all installing dependencies.