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JavaScript

Jason Nelson
Jason Nelson
6,209 Points

randomNumber question.

In the random number extra credit, I'm stuck on this code:

var input= prompt(" Please type a number");
var topNumber =parseInt(input);
var randomNumber = Math.floor(Math.random()*topNumber)+1;

I'm actually confused on the +1, random can give you anything between 0-1 not including 1. Math.floor rounds down what does the +1 do besides just add 1 to the floor number?

example: Math.floor(0.345)6+1 Math.floor(3.07) 3

Is this correct?

2 Answers

Shawn Flanigan
PLUS
Shawn Flanigan
Courses Plus Student 15,815 Points

Jason,

I reformatted your question a bit to show the code properly. To try to answer your question, let's break the process down a bit.

You're right that Math.random() will give you a number between 0 and 1, not including 1 (to be more specific, it will return a value between 0 and 0.9999999999999999).

When you multiply this random number by your topNumber, you will never actually reach your topNumber. For example, if your topNumber is 10, when you multiply your two numbers, you'll reach a maximum value of 9.999999999999999.

Since you're using Math.floor() to round your results down, the maximum value you'll get from this equation is 9.

Your minimum value will be 0 * 10, or 0.

If you're trying to generate a number between 1 and your maxNumber, adding 1 will do the trick nicely.

Hope this makes sense!

Jason Nelson
Jason Nelson
6,209 Points

Ahh, thanks for the breakdown!