Dart allows for arbitrary precision integers, while JavaScript has a max. Code that works in the VM will not work in JavaScript. This will be a surprise to many developers.

Example:

var bigInt = 346538465234590347592847298346243459756895347698465298346583746592374652378462347569234765834765947569827346583465243765923847659234765928347659567398475647495873984572947593470294387093493456870849216348723763945678236420938467345762304958724596873045876234572037862934765294365243652548673456705673465273465246734506873456729457623845623456234650457693475603768922346728346256;
  print(bigInt); // correct in Dart VM, Infinity in JavaScript

The code from Frog:

var bigInt = (346538465234590347592847298346243459756895347698465298346583746592374652378462347569234765834765947569827346583465243765923847659234765928347659567398475647495873984572947593470294387093493456870849216348723763945678236420938467345762304958724596873045876234572037862934765294365243652548673456705673465273465246734506873456729457623845623456234650457693475603768922346728346256);
  print(bigInt);

How do we handle differences like this, and communicate it to the developer?