Generate Random Whole Numbers with JavaScript

You can generate random decimal numbers with Math.random(), but sometimes you need to generate random whole numbers. The following process will give you a random whole number less than 20:

1. Use Math.random() to generate a random decimal number.
2. Multiply that random decimal number by 20.
3. Use Math.floor() to round this number down to its nearest whole number.

Remember that Math.random() can never quite return a 1, so it's impossible to actually get 20 since you are rounding down with Math.floor(). This process will give you a random whole number in the range from 0 to 19.

Putting everything together, this is what your code looks like:

Math.floor(Math.random() * 20);

You are calling Math.random(), multiplying the result by 20, then passing the value to Math.floor() to round the value down to the nearest whole number.

Use this technique to generate and return a random whole number in the range from 0 to 9.