# JS-Interpreter Backwards Stepping Demo

The intepreter may be stepped forwards like a debugger. Additionally, by saving a stack of serializations, the interpreter may also be stepped backwards.

Since each serialization consumes about 300 kb of memory, this demo uses Diff Match Patch to only store the deltas between each step.

Click Parse, then click Step ← and/or Step → repeatedly. Open your browser's console for errors.

var a = prompt('First Number', '1'); var b = prompt('Second Number', '2'); var sum = Number(a) + Number(b); alert('Sum: ' + sum);

Back to the JS-Interpreter documentation.