When npm prestart is Executed

The package.json file allows us to specify a “prestart” script.
When does the npm prestart script run?
The entry under “prestart” will run first when “start” is called, before the script specified by “start“.

The example below demonstrates this.

package.json:

{
  "name": "example-repo",
  "scripts": {
    "prestart": "echo 'In prestart...'",
    "start": "node index.js"
  }
}

Running start:

$ npm run start

Output:

> prestart
> echo 'In prestart...'

In prestart...

> start
> node index.js

This can be useful to run scripts required as a pre-requisite for running a build, for example.