These assignments are polluting the global namespace. If you open up a JavaScript console, you can see that all of these variables exist and are available to any JavaScript that runs. In most cases this is not a problem, but its possible that some external library might execute `increment = 0` (increment being a common name) which would cause the debt counter to stop increasing. In general its a bad practice to make variables like these globally available. Instead, you want to wrap this code in a function. Wrapping in a function means these variables are local to the function only.

```
(function() {
  var amount = document.getElementById('current-debt');
  ... do stuff
})();
```

It creates the function and executes it immediately and if you open a JavaScript console all these variables are unavailable globally.