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Package.json Conventions

The following applies to the “scripts” section of package.json files.

Names

npm script names MUST contain only lower case letters, : to separate parts, - to separate words, and + to separate file extensions. Each part name SHOULD be either a full English word (e.g. coverage not cov) or a well-known initialism in all lowercase (e.g. wasm).

Here is a summary of the proposal in EBNF.

name = life-cycle | main ":fix"? target? option* ":watch"?

life-cycle = prepare | preinstall | install | postinstall | prepublish | preprepare | prepare | postprepare | prepack | postpack | prepublishOnly;

main = "build" | "lint" | "start" | "test";

target = ":" word ("-" word)* | extension ("+" extension)*;

option = ":" word ("-" word)*;

word = [a-z]+;

extension = [a-z0-9]+;

Order

The script names MUST appear in the package.json file in alphabetical order. The other conventions outlined in this document ensure that alphabetical order will coincide with logical groupings.

Main Script Names

With the exception of npm life cycle scripts all script names MUST begin with one of the following names.

Build

Scripts that generate a set of files from source code and / or data MUST have names that begin with build.

If a package contains any build:* scripts, there MAY be a script named build. If so, SHOULD produce the same output as running each of the build scripts individually. It MUST produce a subset of the output from running those scripts.

Lint

Scripts that statically analyze files (mostly, but not limited to running eslint itself) MUST have names that begin with lint.

If a package contains any lint:* scripts, there SHOULD be a script named lint and it MUST run all of the checks that would have been run if each lint:* script was called individually.

If fixing is available, a linter MUST NOT apply fixes UNLESS the script contains the :fix modifier (see below).

Start

A start script is used to start a server. As of this writing, no ESLint package has more than one start script, so there’s no need start to have any modifiers.

Test

Scripts that execute code in order to ensure the actual behavior matches expected behavior MUST have names that begin with test.

If a package contains any test:* scripts, there SHOULD be a script named test and it MUST run of all of the tests that would have been run if each test:* script was called individually.

A test script SHOULD NOT include linting.

A test script SHOULD report test coverage when possible.

Modifiers

One or more of the following modifiers MAY be appended to the standard script names above. If a target has modifiers, they MUST be in the order in which they appear below (e.g. lint:fix:js:watch not lint:watch:js:fix)

Fix

If it’s possible for a linter to fix problems that it finds, add a copy of the script with :fix appended to the end that also fixes.

Target

The name of the target of the action being run. In the case of a build script, it SHOULD identify the build artifact(s), e.g. “javascript” or “css” or “website”. In the case of a lint or test script, it SHOULD identify the item(s) being linted or tested. In the case of a start script, it SHOULD identify which server is starting.

A target MAY refer to a list of affected file extensions (such as cjs or less) delimited by a +. If there is more than one extension, the list SHOULD be alphabetized. When a file extension has variants (such as cjs for CommonJS and mjs for ESM), the common part of the extension MAY be used instead of explicitly listing out all of the variants (e.g. js instead of cjs+jsx+mjs).

The target SHOULD NOT refer to name of the name of the tool that’s performing the action (eleventy, webpack, etc.)

Options

Additional options that don’t fit under the other modifiers.

Watch

If a script watches the filesystem and responds to changes, add :watch to the script name.