node/deps/npm/lib/update.js

/*
for each pkg in prefix that isn't a git repo
  look for a new version of pkg that satisfies dep
  if so, install it.
  if not, then update it
*/

module.exports = update

update.usage = "npm update [pkg]"

var npm = require("./npm.js")
  , asyncMap = require("slide").asyncMap
  , log = require("npmlog")

  // load these, just so that we know that they'll be available, in case
  // npm itself is getting overwritten.
  , install = require("./install.js")
  , build = require("./build.js")

update.completion = npm.commands.outdated.completion

function update (args, cb) {
  npm.commands.outdated(args, true, function (er, outdated) {
    if (er) return cb(er)

    var wanted = outdated.filter(function (ww) {
      var dep = ww[1]
      var current = ww[2]
      var wanted = ww[3]
      var latest = ww[4]
      if (current === wanted && wanted !== latest) {
        log.verbose(
          'outdated',
          'not updating', dep,
          "because it's currently at the maximum version that matches its specified semver range"
        )
      }
      return current !== wanted
    })
    if (wanted.length === 0) return cb()

    log.info('outdated', 'updating', wanted)
    asyncMap(wanted, function (ww, cb) {
      // [[ dir, dep, has, want, req ]]
      var where = ww[0]
        , dep = ww[1]
        , want = ww[3]
        , what = dep + "@" + want
        , req = ww[5]
        , url = require('url')

      // use the initial installation method (repo, tar, git) for updating
      if (url.parse(req).protocol) what = req
      npm.commands.install(where, what, cb)
    }, cb)
  })
}