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JavaScript

Posted by Nas Jones
Nas Jones
7,849 Points

Function

Hello i'm still just learning JS. When i saw this function in a video it confused me. I asked about this before some guy explained it to me in a complicated way. Can someone simply explain it to me?. function getRandomNumber(upper) { return Math.floor( Math.random() * upper ) + 1; }

Conor Vanoystaeyen
Conor Vanoystaeyen
16,687 Points

This can help. Run the code a few times, and you will see how it works.

function getRandomNumber(upper) { 
  console.log("first just random---------------------");
  let num = Math.random();
  console.log(num);
  console.log("second random * upper---------------------");
  let numx = Math.floor( num * upper );
  console.log(numx);
  console.log("third random * upper + 1---------------------");
  console.log(numx + 1);
}

1 Answer

Conor Vanoystaeyen
Conor Vanoystaeyen
16,687 Points

This function will give back a random number between 0 and the upper. So to break it down Math.floor(returns the largest integer less than or equal to a given number) and Math.random(returns a floating-point, pseudo-random number in the range 0 to less than 1 (inclusive of 0, but not 1)) so if you won't more than 0 you do (* upper) bet than you don't get the max (you pick 9 max return = 8) so you do +1.

More info: → https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor → https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random

Nas Jones
Nas Jones
7,849 Points

I'm still kind of confused, i'm going to explain what i understand and you can correct me if im wrong. Upper is the given number we give it so lets say 10. How would that work out in this part of the code Math.floor( Math.random() * upper ) + 1; } . Math.random is a number between 0 and 1 but not 1 so lets say it comes out to 0.5 multiply that by the upper which i said was 10 that's 5. Then math.floor would return 5 since 5 is equal to 5. Then the plus 1 so the random number is 6 in my example here?

Conor Vanoystaeyen
Conor Vanoystaeyen
16,687 Points

yes that should be correct