Here I want to show you a tip for creating a random number between 1 and N in easiest and shortest way.
Here is the code:
~~(Math.random() * N) + 1
All you need to do is to replace N with your upper number.
Math.random() which creates a random number between 0 and 1, e.g. 0.3577353348955512. We use this function to have a random number, then we multiply that to our upper number (e.g. 6):
0.3577353348955512 * 6 = 2.1464120093733072
And then we get the floor number with double
~ operator (see this tip: https://coderwall.com/p/9b6ksa).