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JavaScript JavaScript Basics (Retired) Working With Numbers Create a random number

Posted by wilton cruz
wilton cruz
5,917 Points

Random Numbers in JavaScript Math.random() at the Mozilla Developer Network

why random to six,why not to seven and Up?

or is it because he multiplied by 6?

help with this please!,and thanks in advance.

Kelvin Simon
Kelvin Simon
6,209 Points

If you want a number higher than 6 the yes you can just replace 6 with a different number. For example

Math.floor((Math.random() * 10) + 1);

this would produce a number between 1 & 10

1 Answer

bothxp
bothxp
16,510 Points

Hi wilton,

Math.random() returns a floating point number from 0 up to but not including 1. For example:

> Math.random()
0.2625259844878184
> Math.random()
0.06513541210374607
> Math.random()
0.5629554153276711

So that is great if you want a decimal number between 0 and 1, but normally you will want a larger number. To do this you can multiply Math.random() by a number. If we wanted numbers between 0 & up to but not including 100:

> Math.random() * 100
26.25259844878184
> Math.random() * 100
6.513541210374607
> Math.random() * 100
56.29554153276711

Often you will want a whole number, for that we can use Math.floor() which will strip off the numbers after the decimal:

> Math.floor( Math.random() * 100 )
26
> Math.floor( Math.random() * 100 )
6
> Math.floor( Math.random() * 100 )
56

Math.floor( Math.random() * 100 ) will return the numbers 0,1,2,3,4,5 ...... 97,98,99.

If you wanted numbers between 1 & 100 then you would need to + 1. So it becomes 

Math.floor( Math.random() * 100 ) + 1

In the video Dave just used 6 as an example, but you can use what ever number you wanted.