get-fields.js

function getFields(array, fields = []) {
  return array.map(item =>
    fields.length === 1
      ? item[fields[0]]
      : new Array(fields.length).fill(null).map((_, i) => item[fields[i]])
  )
}

// How to use?
const arr = [{ id: 1, name: "Steve" }, { id: 2, name: "Bill" }]
getFields(arr, ["id"])           // [1, 2]
getFields(arr, ["id", ["name"]]) // [[1, 'Steve'], [2, 'Bill']]