step

Walk it, one transition at a time

Nothing here is graded. The panes show the machine at one step index and move together; stepping back re-runs the program from the start, so what you see at step 12 is exactly what was there the first time.

After the third line, what is in `a`?

1const a = [1, 2];
2const b = a;
3b.push(3);
4console.log(a.length, a === b);