# Check if a Number is a Float or Integer in JavaScript

## Introduction

If you're trying to validate user input, for example, figuring out how to determine the type of a number in JavaScript is a problem you may come across. In this Byte, we're going to explore how to check whether a number is an integer or a floating-point number.

## JavaScript Number Types

You may not have known this, but in JavaScript, all numbers are treated as floating-point numbers, regardless of whether they have decimal places or not. This is because JavaScript follows the IEEE 754 standard for Binary Floating-Point Arithmetic. This might seem a bit confusing if you're coming from a language that distinguishes between integers and floating-point numbers internally, but it's one of the quirks of JavaScript that we've come to know and love.

## Why Check for Integer or Float?

There are quite a few reasons we'd want to know if a number is an integer or floating point. One possibility is if we're building a feature that requires integer input. Or, a more obvious use-case, you're validating user input and need to ensure that it's a specific type of number. In these cases, being able to check the type of a number can is needed.

## How to Check if a Number is an Integer in JavaScript

To check if a number is an integer in JavaScript, you can use the `Number.isInteger()`

function. Here's how it works:

```
console.log(Number.isInteger(10)); // true
console.log(Number.isInteger(10.5)); // false
```

In this simple example, we're testing the numbers 10 and 10.5 to see if they're integers. As expected, `Number.isInteger()`

returns `true`

for 10 and `false`

for 10.5.

The `Number.isInteger()`

function only returns `true`

if the value is a number that does not have a decimal component. It will return `false`

for non-numeric values.

But what if we want to check if a number is an integer in a string? Well, we can parse the string to a number using `parseFloat()`

and then check if it's an integer:

```
let num = "10";
console.log(Number.isInteger(parseFloat(num))); // true
```

In this case, `parseFloat()`

converts the string "10" to the number 10, and `Number.isInteger()`

correctly identifies it as an integer.

## How to Check if a Number is a Float in JavaScript

In JavaScript, there's no specific type for floats. Both integers and floats are considered as `Number`

type. However, we can still determine if a number is a float.

Here's a clever function that checks if a number is a float:

```
function isFloat(n) {
return Number(n) === n && n % 1 !== 0;
}
```

This function works by checking if the input is indeed a number (`Number(n) === n`

) and that the remainder of the division of `n`

by `1`

is not `0`

(`n % 1 !== 0`

). If the remainder is not `0`

, it implies that `n`

has a fractional component, hence a float.

For example:

```
console.log(isFloat(10.5)); // Returns: true
console.log(isFloat(10)); // Returns: false
```

## Handling Edge Cases

While the function above works for most cases, there are some edge cases we need to consider. For example, what happens if we pass a string that can be converted to a number? Or what if we pass an array?

Let's improve our function to handle these edge cases:

```
function isFloat(n) {
if (typeof n !== 'number') {
return false;
}
return Number(n) === n && n % 1 !== 0;
}
```

Now, our function will first check if the input is a number type. If not, it immediately returns `false`

. This way, we can prevent incorrect results from invalid inputs.

For example:

```
console.log(isFloat("10.5")); // Returns: false
console.log(isFloat([10.5])); // Returns: false
```

## Precision and Limitations

Because of the IEEE 754 standard, JavaScript can only safely represent numbers between -(2^{53} - 1) and 2^{53} - 1. Any number outside of this range might lose precision.

Moreover, due to the binary floating-point representation, some decimal numbers can't be represented exactly. This can lead to unexpected results when comparing numbers or checking if a number is a float.

You may have seen this odd example floating around the web:

```
console.log(0.1 + 0.2 === 0.3); // Returns: false
```

We get `false`

because of this:

```
console.log(0.1 + 0.2); // Returns: 0.30000000000000004
```

Therefore, when working with floats in JavaScript, you'll always need to be aware of these limitations and handle them appropriately in your code.

## Conclusion

In this Byte, we've learned how to check if a number is a float in JavaScript. We've also seen how to handle edge cases and talked about the limitations of number precision in JavaScript. While JavaScript doesn't have a specific float type, we can still determine if a number is a float by checking the remainder of its division by 1.

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