Script to choose between yarn or npm.

yarnOrNpm.js

const path = require('path')
const spawn = require('cross-spawn')
const execSync = require('child_process').execSync

const root = path.resolve('project')
let command
let args = []

try {
  execSync('yarn -v', { stdio: 'ignore' })
  command = 'yarn'
  args = args.concat(['--cwd', root, 'add'])
} catch {
  command = 'npm'
  args = args.concat(['--prefix', root, 'install'])
}

const devDependencies = ['chalk']
const commandOptions = ['-D', '-E']
args = args.concat(commandOptions, devDependencies)

spawn.sync(command, args, { stdio: "inherit" })