bool every( test(E element))

Checks whether every element of this iterable satisfies test.

Checks every element in iteration order, and returns false if any of them make test return false, otherwise returns true.

Source 

bool every(bool test(E element)) {
  int length = this.length;
  for (int i = 0; i < length; i++) {
    if (!test(this[i])) return false;
    if (length != this.length) {
      throw new ConcurrentModificationError(this);
    }
  }
  return true;
}