simple-email/node_modules/npm/doc/cli/npm-ci.md

npm-ci(1) -- Install a project with a clean slate

SYNOPSIS

npm ci

EXAMPLE

Make sure you have a package-lock and an up-to-date install:

$ cd ./my/npm/project
$ npm install
added 154 packages in 10s
$ ls | grep package-lock

Run npm ci in that project

$ npm ci
added 154 packages in 5s

Configure Travis to build using npm ci instead of npm install:

# .travis.yml
install:
- npm ci
# keep the npm cache around to speed up installs
cache:
directories:
- "$HOME/.npm"

DESCRIPTION

This command is similar to npm-install(1), except it's meant to be used in automated environments such as test platforms, continuous integration, and deployment. It can be significantly faster than a regular npm install by skipping certain user-oriented features. It is also more strict than a regular install, which can help catch errors or inconsistencies caused by the incrementally-installed local environments of most npm users.

In short, the main differences between using npm install and npm ci are:

• The project must have an existing package-lock.json or npm-shrinkwrap.json.
• If dependencies in the package lock do not match those in package.json, npm ci will exit with an error, instead of updating the package lock.
• npm ci can only install entire projects at a time: individual dependencies cannot be added with this command.
• If a node_modules is already present, it will be automatically removed before npm ci begins its install.
• It will never write to package.json or any of the package-locks: installs are essentially frozen.

SEE ALSO

• npm-install(1)
• npm-package-locks(5)