 # How to Validate Decimal Number in JavaScript

While working with web development, there may be situations where we need to parse a string/number and verify if it is a decimal number or not. In this article, we will learn how to validate decimal number in JavaScript.

## How to Validate Decimal Number in JavaScript

By default, most developers use isNumeric() function to determine if a string/number is decimal number or not.

`isNumeric(n)`

But isNumeric() function fails in many use cases as shown below.

```// Whitespace strings:
IsNumeric(' ')    == true;
IsNumeric('\t\t') == true;
IsNumeric('\n\r') == true;

// Number literals:
IsNumeric(-1)  == false;
IsNumeric(0)   == false;
IsNumeric(1.3) == false;
IsNumeric(9e5) == false;```

So we need to make use of two JS functions for this purpose isNaN(), parseFloat() and isFinite(). parseFloat() parses an argument and returns a floating point number. isNaN() checks if a given value is NAN (Not a Number), which can be the result of parseFloat() in case the input is not a number. We also use isFinite() function to determine if it is not infinite. Combining these you can check if a number n is decimal or not as shown below.

`return !isNaN(parseFloat(n)) && isFinite(n);`

You can create your own isNumeric() function incorporating the above expression.

```function isNumeric(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
//e.g isNumeric(4.5) returns true```

In this article, we have learnt how to validate decimal number in JavaScript. It can be used for data validation in your website or web applications.