# JavaScript Math.floor() Method

Shubham Vora Jan 30, 2023

In JavaScript, `Math.floor()` is a built-in library method used to round down the numbers to the nearest integer value. In simple terms, the `Math.floor()` method removes the decimal part of the number and gives the integer part as an output.

## Syntax of JavaScript `Math.floor()` Method

``````Math.floor(x);
``````

### Parameters

`x` - Any numeric value or expression.

### Return

The `Math.floor()` method returns the nearest largest integer smaller than or equal to `x`.

## Example 1: Use the `Math.floor()` Method to Round Down Numbers

In the example below, we have taken 4 different numeric values to round down using the `Math.floor()` method.

In the example output, users can observe that it returns the integer part of the numeric values. Even if 0.99 is nearest to 1, the method returns 0 as an output as we are rounding down the number.

``````let num = 1.1;
console.log(Math.floor(num));
console.log(Math.floor(4.51));
console.log(Math.floor(0.99));
console.log(Math.floor(10));
``````

Output:

``````1
4
0
10
``````

## Example 2: Use the `Math.floor()` Method on a String Value

In general, `Math.floor()` is used with numeric values, but in some cases, if we use it with string values, it returns `NaN` (Not a Number). Users can see the output for the different string values below.

``````let string = "Delft";
Math.ceil(string);
console.log(Math.floor(string));
console.log(Math.floor("Hello"));
``````

Output:

``````NaN
NaN
``````

## Example 3: Use the `Math.floor()` Method on Addition of Two Values

We can use the `Math.floor()` method to round down numbers after performing different operations on multiple numbers.

In the example below, we will add two numbers and round them down using the `Math.floor()` method. Also, we will round down both numbers separately first, add them, and observe the output.

``````let number1 = 3.2;
let number2 = 5.99;
let sum1 = Math.floor(number1+number2);
let sum2 = Math.floor(number1) + Math.floor(number2);
console.log(sum1);
console.log(sum2);
``````

Output:

``````9
8
``````

## Example 4: Use the `Math.floor()` Method on an Empty Value

Users can apply the `Math.floor()` method to empty values. We will take the different types of empty values and observe the output of `Math.floor()` using the below example.

In the output, users can see that for the `null` and empty string `""`, the method always returns 0 instead of `NaN`. When we pass the positive or negative `Infinity` as a parameter of the `Math.floor()` method, it always returns the same value.

For the `undefined`, and `NaN` values, `Math.floor()` method returns `NaN` (Not a Number) value.

``````console.log(Math.ceil(null));
console.log(Math.ceil(""));
let val = -Infinity;
let floorValue = Math.floor(val);
console.log(floorValue);
let num = undefined;
console.log(Math.ceil(num));
console.log(NaN);
``````

Output:

``````0
0
-Infinity
NaN
NaN
``````

## Example 5: Use `Math.floor()` and `Math.round()` to Get and Compare the Rounded Numbers

In this example, we will use the `Math.floor()` and `Math.round()` methods to compare the output and see the difference between both.

In the example output, users can see that the `Math.floor()` method always rounds down the number, but the `Math.round()` method either rounds up or down the number according to the nearest integer value.

``````let number = 1.99;
console.log(Math.floor(number));
console.log(Math.round(number));
console.log(Math.floor(-1.49));
console.log(Math.round(-1.49));
``````

Output:

``````1
2
-2
-1
``````

The `Math.floor()` method is supported in all browsers. This article has explored different use cases of the `Math.floor()` method.

Author: Shubham Vora

Shubham is a software developer interested in learning and writing about various technologies. He loves to help people by sharing vast knowledge about modern technologies via different platforms such as the DelftStack.com website.