The JavaScript `Math.floor()`

method is a part of the Math object that you can use to round a decimal number down. For example, a number variable of `7.2`

will be rounded down to `7`

when you pass it into the method.

The syntax for this method looks as follows:

```
Math.floor(7.2); // returns 7
```

You can pass the initial number as a variable:

```
let score = 7.2;
Math.floor(score); // returns 7
```

Or store the returned number in a variable like this:

```
let score = 7.2;
let roundedScoreDown = Math.floor(score);
console.log(roundedScoreDown); // 7
```

The method accepts only one parameter of `number`

value. If you pass a `string`

, an `object`

, or an `array`

to the method, it will return `NaN`

which stands for `Not a Number`

:

```
Math.floor("Hello there!");
Math.floor([1, 2, 3]);
Math.floor({ name: "Andy" });
// returns NaN
```

When you pass a `boolean`

value of `true`

or `false`

it will return `1`

for `true`

and `0`

for `false`

:

```
Math.floor(true);
// returns 1
Math.floor(false);
// returns 0
```

Remember to use dot (`.`

) when you pass in a decimal number because a comma (`,`

) in JavaScript parameters is an indicator of separate variables. In the following example, JavaScript will simply floor the first number and ignore the second when you pass two numbers:

```
Math.floor(9, 2);
// returns 9
```

Finally, the Math.floor() method will round a number down no matter if the decimal value is `.5`

or higher:

```
Math.floor(8.5);
// returns 8
```

## Using Math.floor() on negative numbers

The method will also round a negative number down. Negative numbers get smaller the farther they are from zero, so the number value of `-55.2`

will be rounded to `-56`

and not `-55`

:

```
Math.floor(-55.2)
// returns -56
```

## Other Math rounding method

Finally, if you want to round the number up when its decimal value is higher than `.5`

then you need to use `Math.round()`

method.

When you want to round the number up instead of down (from `7.2`

to `8`

) then you need to use [the `Math.ceil()`

method]( {{ <ref “/18-javascript-math-ceil”> }} ).