### Introduction

In this article, we'll be taking a look at

how to round a number to an integer (whole number) in JavaScript.

JavaScript provides three different methods to achieve this goal: the `round()`

method, the `ceil()`

method and the `floor()`

method.

All of these are static methods of the `Math`

object. This means that they will be called directly via `Math.method_name()`

, not as a method of an instance of `Math`

object - `Math`

has no constructor.

**Note:** These methods can only be called on numbers, everything else will result in a `NaN`

value. The only exception is when it's called on `null`

- calling methods on `null`

will always return 0.

### The *ceil()* Method

The name of this method is actually an abbreviation of the word *ceiling* - so its name automatically rings a bell that it *rounds a number to the closest integer value larger than the current number*.

If the number is an integer already - there's nothing to round, so it'll simply return the integer instead:

```
let x = 4.7
console.log(Math.ceil(x))
// Output: 5
let y = -3.2
console.log(Math.ceil(y))
// Output: -3
let z = "something not a number"
console.log(Math.ceil(z))
// Output: NaN
console.log(Math.ceil(null))
// Output: 0
```

You'll use `ceil()`

when you *specifically* want to round to the next upper bound. `5.1`

is rounded to `6`

, so if you want to round to the *closest* integer, you'll use the `round()`

function, covered in a later section of this guide.

### The *floor()* Method

Similar to `ceil()`

, `floor()`

's method is also carefully chosen to fit its purpose. It rounds the integer to the closest integer smaller than the current one:

```
let x = 4.7
console.log(Math.floor(x))
// Output: 4
let y = -3.2
console.log(Math.floor(y))
// Output: -4
let z = "something not a number"
console.log(Math.floor(z))
// Output: NaN
console.log(Math.floor(null))
// Output: 0
```

### The *round()* Method

The `round()`

method can be viewed as a two-in-one method, containing both `ceil()`

and `floor()`

. It rounds the number to the closest integer - it either *"ceils"* the number, or *"floors"* it, based on its value:

```
let x = 4.7
console.log(Math.round(x))
// Output: 5
let y = 4.2
console.log(Math.round(y))
// Output: 4
let z = 4.5
console.log(Math.round(z))
// Output: 5
console.log(Math.round(null))
// Output: 0
```

Everything up to *x.49* will be rounded down to the lower value, while everything higher than that will be rounded to the higher value.

### Conclusion

In this quick article, we had a look at some of the methods that can be used to round a non-integer in JavaScript. Some key notes to take away from this article are:

- Math.ceil() - rounds the number to a
*higher*value - Math.floor() - rounds the number to a
*lower*value - Math.round() - rounds the number to either lower or higher value,
*depending on the number* - When called with
`null`

as an argument, the methods always return 0 - When called with anything but a number or null as an argument, the methods always return
`NaN`