Your original question asked about showing variable values and you mentioned the console; that's what console.log() does. These console.log() statements are used in debugging to send outputs from key steps in a process to the console which you can look at once the code has executed. You can have many console.log() statements in a single script to output any many key values as you like while the process runs.
Perhaps you could explain a bit more about what you mean by "copying variables onto the screen"