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JavaScript JavaScript Basics (Retired) Creating Reusable Code with Functions Random Number Challenge, Part II Solution

kabir k
PLUS
kabir k
Courses Plus Student 18,036 Points
Posted by kabir k
kabir k
Courses Plus Student 18,036 Points

Is my function also correct?

I am curious about the version of my code for the flexible random number generating function.

Here's the Teacher's version:

function getRandomNumber(lower, upper) {
  return Math.floor(Math.random() * (upper - lower + 1)) + lower;
}
alert(getRandomNumber(2, 9));

And here's my version:

function getRandomNumber(lower, upper) {
  return Math.floor(Math.random() * upper ) + lower;
}
alert(getRandomNumber(2, 9));

My questions are:

  1. Is there a difference between the two and if there is, what is the difference and is my version also correct?

  2. If my version is also correct, why are we subtracting lower from upper in the Teacher's version?

1 Answer

Jasper van der Stoop
Jasper van der Stoop
2,214 Points
Jasper van der Stoop
Jasper van der Stoop
2,214 Points

Yes, there is a clear difference between the two. To help you understand everything better:

Math.random();

Returns a random float between 0 and 1, with 1 being excluded.

Math.floor();

Returns the closest integer, rounding down.

Now what the teacher does, is creating a function that gets a random number between 2 and 9. To do this, he takes the difference between the two numbers and adds one. This number times a random value between 0.00-0.99, will leave you with something between 0.00 and 7.99. Adding the base number 2, will give 2.00-9.99. If you floor this value, you will get a integer between 2 and 9.

With your method, you can get anything between 2.00-11.99. Thus, your function is invalid.