Error for creating a simple random number

So I am trying to set a simple variable as a random number, but I keep getting an error. I'm using https://thimble.mozilla.org/ to run my code but it keeps giving me an error.

my code is:

    var x = randomNumber(1,6)

    console.log(x);

I've tried putting in and taking out a semicolon at the end of line 1