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: ['[email protected]', '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)
})