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:
Classification
- Natively supported scripts
- 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 into Lifecycle, Action-specific, Command-specific scripts.
1-1 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:
See more here.
1-2 Action-specific scripts
Description
Run in the flow of one npm command along with command's main action. Some scripts run in more than one commands those perform related actions.
Scripts
- prepublish - in flow of
npm ci,npm install - prepublishOnly - in flow of
npm publish - prepack/postpack - in flow of
npm pack,npm publish - preinstall/install/postinstall - in flow of
npm ci,npm install,npm rebuild - preversion/version/postversion - in flow of
npm version
Example
npm version commands run the flow that includes its main action and predefined scripts. Execution order:
- preversion script
- npm version command's action
- version script
- postversion script
See more here.
1-3 Command-specific scripts
Description
Run in response of exactly one built-in npm command. These commands don't have their own actions and only run predefined scripts
Scripts
- prestart/start/poststart - in response of
npm start - prerestart/restart/postrestart - in response of
npm restart - prestop/stop/poststop - in response of
npm stop - pretest/test/posttest - in response of
npm test
Example
npm start performs the next operations in order:
- 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 may be other ways to perform developer-defined tasks, but it's handy to use npm ecosystem for them
How to define:
package.json, "scripts" object
When executed
In response of npm run command that runs exactly certain script named script-name
How to run
npm run[-script] <script-name>
Important
Arbitrary scripts can have pre/post versions
Example
Given we have precompress, compress and postcompress scripts in package.json.
npm run[-script] compress performs the next:
- precompress script
- compress script
- postcompress script
So arbitrary scripts are similar to Command-specific native scripts. But they don't have a specific built-in npm command for running them.
This was a brief summary about npm scripts. I'm glad to receive a feedback!
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