There's just no mechanism for doing that in vanilla JavaScript. We can't really track the reading and writing of local variables like in the example.

when A0 is assigned a new value, notify all its subscriber effects to re-run. because A0 and A1 are read when update() is being executed, update() becomes a subscriber to both A0 and A1 after the first call.ĭetect when a variable is mutated. If a variable is read when there is a currently running effect, make that effect a subscriber to that variable.

when evaluating the expression A0 + A1, both A0 and A1 are read. This whenDepsChange() function has the following tasks: