install-if-needed

Installs the given list of modules and saves them into their respective fields in your nearest package.json. Dependencies that already exist in your package.json will be skipped.

var install = require('install-if-needed')

install({
  dependencies: ['through2'],
  devDependencies: ['tape@2.x', 'standard']
}, function(err) {
  if (err)
    console.error("There was an error installing.")
})

You can pass { stdio: 'inherit' } to preserve logging and colors, acting like the usual npm install command.

Usage

install(opt[, cb])

Looks at package JSON and installs any of the specified dependencies that are not listed in their respective field.

• cwd the directory for the closest package.json, (default process.cwd())
• package optional package data, if not defined will search for closest package.json
• save whether to --save, --save-dev and --save-optional (default true)
• dependencies dependencies to install
• devDependencies dev dependencies to install
• optionalDependencies optional dependencies to install
• command the command to spawn when installing, defaults to 'npm'

Other options are passed to spawn-npm-install.

On complete, cb is called with (err) status. All dependencies also accept a single string instead of an array.

Alternatively, opt can be a string or array, which is the same as listing it in dependencies.

//e.g.
//  npm install tape --save
install('tape', done)

Motivation

This helps build CLI tooling that auto-installs modules as needed. For example, a tool which stubs out an empty test file for tape:

#!/usr/bin/env node
var install = require('install-if-needed')
var fs = require('fs')
var template = fs.readFileSync(__dirname + '/template.js')

install({
  devDependencies: 'tape'
}, function(err) {
  if (err) throw err
  fs.writeFile(process.argv[2], template)
})

And the CLI might be as simple as:

quick-tape tests/simple.js

License

MIT, see LICENSE.md for details.