getLatestVersion.js

import spawn from 'cross-spawn'
import ora from 'ora'

/**
 * Get the latest version of a package from npm.
 */
export function getLatestVersion(pkg, cb) {
  let spinner = ora(`Checking for latest version of ${pkg}`).start()
  let npm = spawn('npm', ['dist-tag', 'ls', pkg, '--no-progress'], {stdio: ['ignore', 'pipe', 'inherit']})
  let stdout = ''
  npm.stdout.on('data', (data) => { stdout += data })
  npm.on('exit', (code) => {
    if (code !== 0) {
      spinner.fail()
      return cb(new Error('Error running npm dist-tag ls'))
    }
    let match = /^latest: ([^\n]+)/m.exec(stdout.toString('utf-8'))
    if (!match) {
      spinner.fail()
      return cb(new Error('Could not find latest version in dist-tag results'))
    }
    spinner.succeed()
    cb(match[1])
  })
}