Enforce Node version with nvm inside a npm script

Quick tip on how to the correct Node version is used for local development.

Some projects require a specific Node version to work and I might run into an error if I dont do these steps:

# init nvm
source /usr/share/nvm/init-nvm.sh
 
# have node setup and use the correct node version
nvm use 20
 
# start development
npm start

Now you could add a step in your .bashrc or .zshrc to always run nvm use for each directory, but that comes with a tiny performance cost when starting a new shell instance. Ideally the start command of my application should deal with this.

Heres how

1. Create a .nvmrc file that tells nvm which Node version is right.

20

2. Update your npm start package script to run

{
  "name": "myPackage",
  "version": "1.0.0",
  "scripts": {
    "start": "unset npm_config_prefix && source $HOME/.nvm/nvm.sh; nvm use && next start",
  },
}

• without unset npm_config_prefix nvm will throw an error

nvm is not compatible with the “npm_config_prefix” environment variable: currently set to “/usr” Run unset npm_config_prefix to unset it. Found ‘/home/fabian/repos/Joaia/holoai-monorepo/functions/azure-functions/.nvmrc’ with version <20> nvm is not compatible with the “npm_config_prefix” environment variable: currently set to “/usr” Run unset npm_config_prefix to unset it.

• the nvm logic must use the start script, it cant be in something like the prestart command because npm spawns a new shell for each npm script command