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docs: updated scripts docs in using-npm section
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- A continuation of @seanhealy's work

PR-URL: npm#729
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Close: npm#729
Reviewed-by: @darcy Clarke
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Michael Perrotte authored and darcyclarke committed Feb 25, 2020
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Expand Up @@ -10,130 +10,64 @@ description: How npm handles the "scripts" field

### Description

The `"scripts"` property of of your `package.json` file supports a number of built-in scripts and their preset life cycle events as well as arbitrary scripts which can be executed by running `npm run <stage>`. *Pre* and *post* commands with matching names will be run for those as well (e.g. `premyscript`, `myscript`,
`postmyscript`). Scripts from dependencies can be run with `npm explore
<pkg> -- npm run <stage>`.

* `prepublish` (_as of npm@5, `prepublish` is deprecated. Use `prepare` for
build steps and `prepublishOnly` for upload-only._):
* Runs BEFORE the package is packed and published, as well as on local `npm
install` without any arguments. (See below)
* `prepare`:
* Runs both BEFORE the package is packed and published, and on local
`npm install` without any arguments (See below). This is run AFTER
`prepublish`, but BEFORE `prepublishOnly`.
* If a package being installed through git contains a `prepare` script, its
`dependencies` and `devDependencies` will be installed, and the prepare
script will be run, before the package is packaged and installed.
* `prepublishOnly`:
* Runs BEFORE the package is prepared and packed, ONLY on `npm publish`.
(See below.)
* `prepack`:
* Runs BEFORE a tarball is packed (on `npm pack`, `npm publish`, and when
installing git dependencies)
* `postpack`:
* Runs AFTER the tarball has been generated and moved to its final destination.
* `publish`, `postpublish`:
* Runs AFTER the package is published.
* `preinstall`:
* Runs BEFORE the package is installed
* `install`, `postinstall`:
* Runs AFTER the package is installed.
* `preuninstall`, `uninstall`:
* Runs BEFORE the package is uninstalled.
* `postuninstall`:
* Runs AFTER the package is uninstalled.
* `preversion`:
* Runs BEFORE bumping the package version.
* `version`:
* Runs AFTER bumping the package version, but BEFORE commit.
* `postversion`:
* Runs AFTER bumping the package version, and AFTER commit.
* `pretest`, `test`, `posttest`:
* Run by the `npm test` command.
* `prestop`, `stop`, `poststop`:
* Run by the `npm stop` command.
* `prestart`, `start`, `poststart`:
* Run by the `npm start` command.
* `prerestart`, `restart`, `postrestart`:
* Run by the `npm restart` command. Note: `npm restart` will run the
stop and start scripts if no `restart` script is provided.
* `preshrinkwrap`, `shrinkwrap`, `postshrinkwrap`:
* Run by the `npm shrinkwrap` command.

Additionally, arbitrary scripts can be executed by running
`npm run-script <stage>`. *Pre* and *post* commands with matching names will
be run for those as well (e.g. `premyscript`, `myscript`, `postmyscript`).
Scripts from dependencies can be run with
`npm explore <pkg> -- npm run <stage>`.

### Life Cycle

npm commands such as `npm install` and `npm publish` will fire life cycle
hooks as specified in your `package.json` file. These hooks are as follows
for each command.
The `"scripts"` property of of your `package.json` file supports a number of built-in scripts and their preset life cycle events as well as arbitrary scripts. These all can be executed by running `npm run-script <stage>` or `npm run <stage>` for short. *Pre* and *post* commands with matching names will be run for those as well (e.g. `premyscript`, `myscript`, `postmyscript`). Scripts from dependencies can be run with `npm explore <pkg> -- npm run <stage>`.

#### [`npm publish`](/cli-commands/npm-publish)
### Pre & Post Scripts

* `prepublishOnly`
* `prepare`
To create "pre" or "post" scripts for any scripts defined in the `"scripts"` section of the `package.json`, simply create another script *with a matching name* and add "pre" or "post" to the beginning of them.

#### [`npm pack`](/cli-commands/npm-pack)
```json
{
"scripts": {
"precompress": "{{ executes BEFORE the `compress` script }}",
"compress": "{{ run command to compress files }}",
"postcompress": "{{ executes AFTER `compress` script }}"
}
}
```

* `prepack`
### Life Cycle Scripts

#### [`npm install`](/cli-commands/npm-install)
There are some special life cycle scripts that happen only in certain situations. These scripts happen in addtion to the "pre" and "post" script.
* `prepare`, `prepublish`, `prepublishOnly`, `prepack`, `postpack`

* `preinstall`
* Run BEFORE the package is installed
* `install`, `postinstall`
* Run AFTER the package is installed.
**prepare** (since `[email protected]`)
* Runs BEFORE the package is packed
* Runs BEFORE the package is published
* Runs on local `npm install` without any arguments
* Run AFTER `prepublish`, but BEFORE `prepublishOnly`
* NOTE: If a package being installed through git contains a `prepare` script, its `dependencies` and `devDependencies` will be installed, and the prepare script will be run, before the package is packaged and installed.

Also triggers
**prepublish** (DEPRECATED)
* Same as `prepare`

* `prepublish` (when on local)
* `prepare` (when on local)
**prepublishOnly**
* Runs BEFORE the package is prepared and packed, ONLY on `npm publish`.

#### `start`
**prepack**
* Runs BEFORE a tarball is packed (on "`npm pack`", "`npm publish`", and when installing a git dependencies).
* NOTE: "`npm run pack`" is NOT the same as "`npm pack`". "`npm run pack`" is an arbitrary user defined script name, where as, "`npm pack`" is a CLI defined command.

`npm run start` has an `npm start` shorthand.
**postpack**
* Runs AFTER the tarball has been generated and moved to its final destination.

* `prestart`
* `start`
* `poststart`
#### Prepare and Prepublish

#### Prepublish and Prepare
**Deprecation Note: prepublish**

#### Deprecation Note
Since `[email protected]`, the npm CLI has run the `prepublish` script for both `npm publish` and `npm install`, because it's a convenient way to prepare a package for use (some common use cases are described in the section below). It has also turned out to be, in practice, [very confusing](https://github.com/npm/npm/issues/10074). As of `[email protected]`, a new event has been introduced, `prepare`, that preserves this existing behavior. A _new_ event, `prepublishOnly` has been added as a transitional strategy to allow users to avoid the confusing behavior of existing npm versions and only run on `npm publish` (for instance, running the tests one last time to ensure they're in good shape).

Since `[email protected]`, the npm CLI has run the `prepublish` script for both `npm
publish` and `npm install`, because it's a convenient way to prepare a package
for use (some common use cases are described in the section below). It has
also turned out to be, in practice, [very
confusing](https://github.com/npm/npm/issues/10074). As of `[email protected]`, a new
event has been introduced, `prepare`, that preserves this existing behavior. A
_new_ event, `prepublishOnly` has been added as a transitional strategy to
allow users to avoid the confusing behavior of existing npm versions and only
run on `npm publish` (for instance, running the tests one last time to ensure
they're in good shape).
See <https://github.com/npm/npm/issues/10074> for a much lengthier justification, with further reading, for this change.

See <https://github.com/npm/npm/issues/10074> for a much lengthier
justification, with further reading, for this change.
**Use Cases**

#### Use Cases

If you need to perform operations on your package before it is used, in a way
that is not dependent on the operating system or architecture of the
target system, use a `prepublish` script. This includes
tasks such as:
If you need to perform operations on your package before it is used, in a way that is not dependent on the operating system or architecture of the target system, use a `prepublish` script. This includes tasks such as:

* Compiling CoffeeScript source code into JavaScript.
* Creating minified versions of JavaScript source code.
* Fetching remote resources that your package will use.

The advantage of doing these things at `prepublish` time is that they can be done once, in a
single place, thus reducing complexity and variability.
Additionally, this means that:
The advantage of doing these things at `prepublish` time is that they can be done once, in a single place, thus reducing complexity and variability. Additionally, this means that:

* You can depend on `coffee-script` as a `devDependency`, and thus
your users don't need to have it installed.
Expand All @@ -142,8 +76,41 @@ Additionally, this means that:
* You don't need to rely on your users having `curl` or `wget` or
other system tools on the target machines.

### Default Values
### Life Cycle Operation Order

#### [`npm publish`](/cli-commands/npm-publish)

* `prepublishOnly`
* `prepare`
* `prepublish`
* `publish`
* `postpublish`

#### [`npm pack`](/cli-commands/npm-pack)

* `prepack`
* `postpack`

#### [`npm install`](/cli-commands/npm-install)

* `preinstall`
* `install`
* `postinstall`

Also triggers

* `prepublish` (when on local)
* `prepare` (when on local)

#### [`npm start`](/cli-commands/npm-start)

`npm run start` has an `npm start` shorthand.

* `prestart`
* `start`
* `poststart`

### Default Values
npm will default some script values based on package contents.

* `"start": "node server.js"`:
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