How to Check if a Number is a Float in JavaScript

In order to determine if a number if a float in JavaScript, you need to understandthe nature of number representation in the language. Since JavaScript uses IEEE 754 standard for floating-point arithmetic, integers and floats are not distinct types. But there are techniques to differentiate them. We’ll cover them below.

Understanding number representation in JavaScript

In JavaScript, numbers are represented as double-precision 64-bit binary format IEEE 754 values, which means that both integers and floating-point numbers are treated as the same type. This can make it challenging to determine if a number is an integer or a float, as they are not inherently distinguished.

Using the Number object and parseInt

The Number object provides methods that can be used to inspect the characteristics of numeric values. One approach to check if a number is a float is to compare it with its integer part obtained using parseInt.

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

Leveraging parseFloat and strict comparison

Alternatively, parseFloat can be used to ensure the number remains the same when its floating-point representation is parsed from a string. Strict comparison to the original number then reveals its type.

function isFloat(n) {
    return parseFloat(n) === n && !Number.isInteger(n);
}

Utilizing Math.floor or Math.ceil

Mathematical functions like Math.floor or Math.ceil can also be used to check for float numbers by comparing the original number with the result of the floor or ceil operation.

function isFloat(n) {
    return Math.floor(n) !== n;
}

Employing Number.isInteger

A straightforward method provided by ES6 is Number.isInteger, which directly checks if a number is an integer, hence its negation would imply a float.

function isFloat(n) {
    return !Number.isInteger(n);
}