Here in the snippet below is my script to store in a single Array (const store) all the data that I need to exploit in a structured way. In order to use them "simply" afterwards.
console.log(store) displays in the console the desired data structure:
(2) [{…}, {…}]
0: {ID: "freecodecamp", streams: {…}, users: {…}, channels: {…}}
1: {ID: "funfunfunction", channels: {…}, users: {…}, streams: {…}}
console.log(store[0].ID) displays the desired result: "freecodecamp"
However store[0].users, store[0].channels, and store[0].streams outputs undefined.
I don't understand why. While everything works great with store[0].ID
const matchCharUrl = str => str.match(/[^/]/g).join('')
// Twitch.tv API call and settings
// --------------------------------------------------
const twitchAPI = () => {
  // const baseUrl = 'https://api.twitch.tv/kraken' // Twitch API base URL
  const baseUrl = 'https://wind-bow.glitch.me/twitch-api/' // FCC Twitch API Pass-through
  const params = ['users/', 'channels/', 'streams/'] // Twitch API, enabled root
  // suffix (channel or user) identifier
  const identifiers = ['freecodecamp', 'funfunfunction']
  // array with datas that will be exploit in a function ( displayResults() )
  const store = []
  identifiers.forEach((ID, index) => {
    const obj = {ID}
    for(const param of params){
      const urlAPI = baseUrl + param + ID
      fetch(urlAPI, {
        method: 'GET'
      }).then(res => {
        if(res.ok) return res.json()
        throw new Error('Network response error. Status Code:', res.status, res.statusText)
      }).then(data => {
        // Data structure of var store:
        // store = [ {id: freecodecamp, channels: {data}, streams: {data}, users: {data} } ]
        obj[matchCharUrl(param)] = data
      }).catch(err => {
        console.log('Fetch Error:', err)
      })
    }
    store.push(obj)
  })
  console.log(store) // OK
  console.log(store[0]) // OK
  console.log(store[0].ID) // OK
  console.log(store[0].users) // undefined
  console.log(store[0].channels) // undefined
  console.log(store[0].streams) // undefined
  // displayResults(store)
}
twitchAPI()