Function descriptor

lib/web/polyfill.js:362–369

(bitmap, value)

// Property descriptors & Symbol
function descriptor(bitmap, value){
  return {
    enumerable  : !(bitmap & 1),
    configurable: !(bitmap & 2),
    writable    : !(bitmap & 4),
    value       : value
  }
}
function simpleSet(object, key, value){
  object[key] = value;
  return object;