How To Number Validation In Javascript

Validating user input is a crucial step in ensuring the correct functioning of your applications. In this blog post, we will focus on number validation in JavaScript, which is a common requirement when dealing with user-submitted data such as forms.

Checking if a Value is a Number

To validate if a value is a number or not, you can use the isNaN() function. This built-in JavaScript function returns true if the given value is not a number, and false if it is a number.

function isNumber(value) {
    return !isNaN(value);

console.log(isNumber(42)); // true
console.log(isNumber('hello')); // false

Validating a Range of Numbers

If you want to validate if a number falls within a specific range, you can do so by using a simple if statement. Here’s an example:

function isValidNumber(value, min, max) {
    if (isNaN(value)) {
        return false;

    return value >= min && value <= max;

console.log(isValidNumber(42, 1, 100)); // true
console.log(isValidNumber('hello', 1, 100)); // false
console.log(isValidNumber(101, 1, 100)); // false

Using Regular Expressions for Number Validation

Another way to validate numbers in JavaScript is by using regular expressions. This method can be particularly useful if you want to ensure that the user input follows a specific format, such as decimal numbers with a certain number of decimal places.

function isDecimalNumber(value, decimalPlaces) {
    const regex = new RegExp(`^\\d+(\\.\\d{1,${decimalPlaces}})?$`);
    return regex.test(value);

console.log(isDecimalNumber(42, 2)); // true
console.log(isDecimalNumber(42.42, 2)); // true
console.log(isDecimalNumber(42.424, 2)); // false
console.log(isDecimalNumber('hello', 2)); // false


In this blog post, we’ve seen different ways to perform number validation in JavaScript, including checking if a value is a number, validating a range of numbers, and using regular expressions for more complex validation requirements. These techniques can help you ensure that your applications handle user input correctly and maintain the integrity of your data.