Generating Random numbers with Javascript

A quick tutorial on how to generate Random numbers with Javascript. Let's get started:

1) Generating a random number
We make use of the Math 'class' available in Javascript

var randomvar = Math.random();

The result is a decimal number e.g. 0.43209418.


2) Generating a random number with a given range
Say for example, we want a random number to be generated from 1 - 10.

var randomvar = Math.random();
var roundedvar = Math.round(randomvar*10); 

Same logic if you want a number from 1 to 1000.

var randomvar = Math.random();
var roundedvar = Math.round(randomvar*1000); 

3) What if I want a value from a minimum of 5 to 10, instead of 1 to 10?
This involves a bit of logic and mathematics...
First, we need a random generated value.
Then, we multiply this random generated value with the difference of the range boundaries (e.g. randomvalue * (max - min) ).
Finally, we add the rounded value obtained in step 2 with the minimum value.

Not convinced? See code for randomNum function below and try if for yourself:

function randomNum(min,max)
{
var randomvar = Math.random() * (max - min);
var roundedvar = Math.round(randomvar) + min;
alert( roundedvar);
}