Discussion on: Creating 3 Stacks With 1 Array in JavaScript

Oh. I see it now 🤦🏻‍♂️!

It works because of the line immediately preceding that line:

this.sizes[stackNumber]++;

That seems tricky – difficult to come back to later on and immediately understand how those lines work in concert. Perhaps it would be more straight-forward to swap those two lines and add 1 to the indexOfTop instead:

// insert our new value to the top of the stack
this.values[this.indexOfTop(stackNumber) + 1] = value;
// increment our stack size by 1
this.sizes[stackNumber]++;