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JavaScript JavaScript Functions Arrow Functions Function Challenge Solution

Kelsey Donegan
Kelsey Donegan
3,342 Points
Posted by Kelsey Donegan
Kelsey Donegan
3,342 Points

Why does swapping the higher value with the lower value still (mostly) work ?

function getRandomNumber(low, high) { return Math.floor(Math.random() * (high - low + 1)) + low; }

I called with function with the following code

console.log( getRandomNumber(100, 10));

and found that it worked. But then I wondered if it was excluding the values themselves so I narrowed the parameters to

console.log( getRandomNumber(3, 1));

and found that it would only produce the number 2 (unless I just witnessed an insane statistical anomaly.)

It almost makes sense to me, but I'm not fully understanding what's happening here.

1 Answer

mouseandweb
mouseandweb
13,758 Points
mouseandweb
mouseandweb
13,758 Points

Hi Kelsey,

When you declared the function's parameters, the first argument is 'low' and the second argument is 'high'. So when you call the function you would have the low number first and then the high. For example, you wrote

getRandomNumber(low, high)

which would mean the function call for 100 & 10 and 3 & 1 and should like this:

getRandomNumber(10, 100);
getRandomNumber(1, 3);

What you ran was:

getRandomNumber(100, 10);
getRandomNumber(3, 1);

So your higher number was set in place of the lower number for the random set. OK, so why did you keep getting 2 for getRandomNumber(3, 1) ?

// this is the body of the function
Math.floor(Math.random() * (high - low + 1)) + low;
// now we place in the values as you called them using getRandomNumber(3, 1)
Math.floor(Math.random() * (1 - 3 + 1)) + 3;
// reduce the arithmetic
Math.floor(Math.random() * (-2 + 1)) + 3;
// reduce further
Math.floor(Math.random() * (-1)) + 3;
// reduce Math.random()
// Math.random() returns a random number less than one. So let's say 0.89!
Math.floor(0.89 * (-1)) + 3;
// let's now reduce that random floating point number 0.89 with the -1
Math.floor(-0.89) + 3;
// now Math.floor() will return the lowest whole number.
/// Since this number is negative, the floor of -0.89 is -1.
-1 + 3;
// for the last step, we reduce the -1 and 3 by adding them together and we get
2