NPM Scripts summary

This content originally appeared on DEV Community 👩‍💻👨‍💻 and was authored by Denvery

There is an extremely brief but too informative summary about such convenient feature of npm as scripts. So few words, only grouped and classified facts.

Disclamer

Information is relevant for npm v9.2.0

Main purposes of this post

• to introduce classification of scripts
• to summarize important things about npm scripts
• to act as a quick reminder about npm scripts

Prerequisites

The readers should already be familiar with npm scripts feature at least at elementary level. It can be learned from scratch using some other sources:

• DEV.TO post
• DigitalOcean post
• NPM docs

Classification

• Natively supported scripts
  • Lifecycle
  • Action-specific
  • Command-specific
• Arbitrary scripts

1 Natively supported

Purpose

To include developer-defined actions into npm command's flow (e.g., npm pack, npm install)

Where defined

package.json, "scripts" object

When executed

As a part of certain npm command - before or after the main action that performed by this command

How to run

npm <command-name>

Native scripts can be classified more deeply. See that below with examples.

Lifecycle scripts

Description

Wide specific scripts. Run in the flow of several npm commands.

Scripts

• preprepare/prepare/postprepare
• dependencies

Example

prepare script is run in the flow of...
...next commands:

• npm cache add
• npm ci
• npm diff
• npm install
• npm pack
• npm publish
• npm rebuild

Action specific scripts

Description

Run in the flow of exactly one npm command or in several closely related commands.

Scripts

• prepublish/prepublishOnly
• prepack/postpack
• preinstall/install/postinstall
• preversion/version/postversion`

Example

npm version commands run the flow that includes its main action + predefined scripts:

• preversion script
• npm version command's action
• version script
• postversion script

Command specific scripts

Description

Run in response of specific npm commands. These commands don't have their own actions other than running predefined scripts.

Scripts

• prestart/start/poststart
• prerestart/restart/postrestart
• prestop/stop/poststop
• pretest/test/posttest

Example

npm start performs the next:

• prestart script
• start script
• poststart script

This command doesn't have its own action other than scripts running.

2 Arbitrary

Purpose

To perform developer-defined tasks using npm ecosystem.

Motivation

There are other ways to perform developer-defined tasks, but it's very convenient to use npm ecosystem for them.

How to define:

package.json, "scripts" object

When executed

In response of npm command that runs exactly certain script

How to run

npm run[-script] <script-name>

Important

Arbitrary scripts have pre/post versions.

Example

npm run[-script] compress performs the next:

• precompress script
• compress script
• postcompress script

This was a brief summary about npm scripts. I'm glad to receive a feedback!

This content originally appeared on DEV Community 👩‍💻👨‍💻 and was authored by Denvery