Creating a random number inside a range in JavaScript

To generate a random number in the JavaScript, you can just use default random method on Math object:

Math.random();

The above code will generate some random number between 0 and 1 (inclusive of 0, but not 1).

If you only want an integer out of the random method, use the floor method of Math object

Math.floor(Math.random());

But the above code will generate single integer, that's 0.

Generate a random number between 0 and 9(both inclusive)

As you know Math.random() will give you a number between 0 and 0.999999... So multiplying it with 10 will give a number between 0 and 9.99999.... Then use Math.floor to convert the obtained number to integer i.e., the following code will give you any of the 10 integers from 0 to 9

Math.floor(Math.random()*10)

Generate random number between 1 and 10

From the above code it's obvious that you can add 1 to it to generate a random number between 1 and 10.

Math.floor(Math.random()*10)+1
// or
Math.floor((Math.random()+1)*10)

Similarly Math.floor(Math.random()*500)+1 will give you a number between 1 and 500

Use Math.ceil() to even simplify the expression:

Math.ceil(Math.random() * 10)

If you use Math.round(Math.random() * 10), you will get any integer between 0 and 10, including both 0 and 10. So you can get any number out of 11 possible integers, if you use Math.round.

Last Updated on Feb 21, 2020