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Brent Leung
1,389 PointsNegative Numbers
How do we account for users inputting one or two negative numbers?
1 Answer
Philip Enchin
Full Stack JavaScript Techdegree Student 24,726 PointsparseInt() will work just fine with negative numbers.
Typing parseInt(-5) into the console will return -5.
The formula used to generate a random number will also work just fine with negative numbers.
Math.random() returns a number between 0 and 1 (not including 1).
Multiplying that by (topNumber - bottomNumber + 1) will give a number between 0 and the difference between topNumber and bottomNumber + 1, not including bottomNumber. So if our top and bottom numbers are 10 and 1 respectively, the random number will come out between 0 and 9.9999999...
Adding the bottomNumber will raise or lower the entire range so the lowest possible value will be bottomNumber.
So looking at the entire example where bottomNumber = -5 and topNumber = 7:
- Math.floor(Math.random() * (topNumber - bottomNumber + 1) + bottomNumber)
- = Math.floor(Math.random() * (7 - (-5) + 1) + (-5))
- = Math.floor(Math.random() * (13) + (-5))
- = Math.floor([0 ≤ n < 13]) + (-5)) //Range doesn't include 13
- = Math.floor([0-5 ≤ n < 13-5])
- = Math.floor([-5 ≤ n < 8])
- = [-5 ≤ n ≤ 7] //Everything over 7 gets rounded down