length property

int length

Returns the number of objects in this list.

The valid indices for a list are 0 through length - 1.

Implementation 

int get length => JS("int", "#.length", this);
void length= (int value)

Changes the length of this list.

If newLength is greater than the current length, entries are initialized to null.

Throws an UnsupportedError if the list is fixed-length.

Implementation 

set length(int value) {
  throw new UnsupportedError("Cannot resize immutable List.");
}