Tips for golfing in Dart
Variable declaration

Regular variable declaration takes 4 bytes (var) + 2 bytes/variable (i,).
You can declare variables as optional named parameters for your function and shave a few bytes.

f(){var i,j,k;} //Takes 15 bytes
g({i,j,k}){}  //Takes 12 bytes


Note: This doesn't work for non-constant values, for example:

f({i=List}){}  //Works
g({i=[]}){}  //Doesn't work

f({i=0,j=0}){}  //Works
g({i=0,j=i}){}  //Doesn't work