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JavaScript JavaScript Basics (Retired) Working With Numbers The Random Challenge Solution

M Khan
M Khan
7,024 Points
Posted by M Khan
M Khan
7,024 Points

Not pretty clear of the concept about + 1 after Math.random function 

var randomNumber = Math.floor(Math.random() * topNumber) + 1;

Can you pls explain about adding + 1 to the Math.random function

3 Answers

Robert Stewart
Robert Stewart
11,921 Points
Robert Stewart
Robert Stewart
11,921 Points

Because the Math.floor() function will always round down so, if your user enters 2 and you multiply that against the random number 0.49 you'll get 0.98 which then gets rounded down to 0. However, the point is to simulate a random number between 1 and whatever number the user enters so 0 is not allowed. This is a preventative step to ensure the number is never zero. Note: Math.random() generates a number between 0 and 1.

I hope that clears some things up.

Alexandra Edwards
Alexandra Edwards
4,686 Points
Alexandra Edwards
Alexandra Edwards
4,686 Points

Math.random generates a number from 0 up to, but not including 1. Since Math.floor rounds down, it is possible to generate the number 0. To prevent that from happening, you add 1 so if the random number rounded down turns out to be 0, the +1 will change 0 to 1. Does that help?

Nelson J
Nelson J
7,411 Points
Nelson J
Nelson J
7,411 Points

To elaborate to Alexandra Edwards. +1 is added in case the user inputs a zero. By doing so you generate a random number regardless of what the input is. If zero is the input, and Math.random generates a number from 0 and up, but not including 1, then the zero becomes 1 because we added +1 and so the program generates a number between 0 and 1, but if you dont specify that, then the program will not generate a random number because a number from 0 to 0 will always be zero.