# How to generate random numbers in JavaScript

By Atta Ur Rehman Shah (https://attacomsian.com/about). Published Nov 28, 2020, updated Nov 27, 2022. Topics: JavaScript.
Canonical URL: https://attacomsian.com/blog/javascript-generate-random-numbers

> Learn about different ways to generate random numbers in JavaScript.

In JavaScript, you can use the `Math. random()` function to generate a pseudo-random floating number between 0 (inclusive) and 1 (exclusive).

```javascript
const random = Math.random()

console.log(random)
// 0.5362036769798451
```

If you want to get a random number between 0 and 20, just multiply the results of `Math.random()` by 20:

```javascript
const random = Math.random() * 20

console.log(random)
// 15.40476356200032
```

To generate a random whole number, you can use the following `Math` methods along with `Math.random()`:

* `Math.ceil()` — Rounds a number upwards to the nearest integer
* `Math.floor()` — Rounds a number downwards to the nearest integer
* `Math.round()` — Rounds a number to the nearest integer

Let us use `Math.floor()` to round the floating number generated by `Math.random()` to a whole number:

```javascript
const random = Math.floor(Math.random() * 20)

console.log(random)
// 12
```

Now we have learned that how to generate a whole random number, let us write a function that takes in an integer as input and returns a whole number between 0 and the integer itself:

```javascript
const random = (max = 50) => {
    return Math.floor(Math.random() * max)
}

console.log(random(100))
// 66
```

To generate a random number between two specific numbers (`min` included, `max` excluded), we have to update the `random()` method like below:

```javascript
const random = (min = 0, max = 50) => {
    let num = Math.random() * (max - min) + min

    return Math.floor(num)
}

console.log(random(10, 40))
// 28
```

In the above code, we used `(max - min) + min` to avoid cases where the `max` number is less than the `min` number.

To generate a random number that includes both `min` and `max` values, just change `Math.floor()` to `Math.round()`: 

```javascript
const random = (min = 0, max = 50) => {
    let num = Math.random() * (max - min) + min

    return Math.round(num)
}

console.log(random(10, 70))
// 51
```