message: Add definition utils
diff: @@ -74,3 +74,11 @@ export function getUUID () {
  return value.toString(16)
  })
  }
  +
  +export function isDefined<T> (value?: T): value is T {
  + return typeof value !== 'undefined'
  +}
  +
  +export function isUndefined<T> (value?: T): value is undefined {
  + return typeof value === 'undefined'
  +}
  