Debugging

Debugging is a delicate art. In the beginning, it usually is very hard to spot what's wrong with your code. If you are using JavaScript in the browser and it is not behaving as you would expect, step 1 is always to open the console in the browser. Often it will contain errors that can help you further.

If that doesn't solve it, you can log to the console in every step of your code, and also log the variables. This will give you some insight as to what is going on. It might just be that you are relying on a certain variable that happens to be undefined. Or perhaps you are expecting a certain value from a mathematical computation, but you've made an error and the result is something completely different from what you thought. Using console.log() during development to see what's happening is rather common.

Breakpoints

A more professional way to go about debugging is to use breakpoints. This can be done from most browsers and IDEs. You click on...