count.js

// $ yarn add request request-promise
// $ node count userA userB

const request = require('request-promise')

const get = resource => request({
  url: /^https/.test(resource) ? resource : `https://api.github.com/${resource}`,
  headers: {
    'User-Agent': 'GitHub Contrib Counter',
    'Authorization': 'token YOUR_PERSONAL_ACCESS_TOKEN'
  },
  json: true
}).catch(e => {
  console.error(e.message)
})

const flatten = arr => [].concat.apply([], arr)

const count = async () => {
  const orgs = process.argv.slice(2)
  const repos = await Promise.all(orgs.map(o => get(`users/${o}/repos`)))
  const contribs = await Promise.all(flatten(repos).map(r => get(r.contributors_url)))
  console.log(new Set(flatten(contribs).map(u => u.login)).size)
}

count()