function init () {
  var code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
  for (var i = 0, len = code.length; i < len; ++i) {
    lookup[i] = code[i]
    revLookup[code.charCodeAt(i)] = i
  }

  revLookup['-'.charCodeAt(0)] = 62
  revLookup['_'.charCodeAt(0)] = 63
}
Crude, but effective.
@api
@param {*} value
@returns {boolean} Whether or not `value` is a Promise