Validate Decimal Numbers in Javascript – Isnumeric()

When working with user input in JavaScript, it is important to validate the data to ensure it meets the required format. One common validation task is to check if a given input is a valid decimal number.

In JavaScript, there is no built-in function to directly check if a string is a valid decimal number. However, we can use regular expressions or built-in JavaScript functions to achieve this.

Using Regular Expressions

Regular expressions are a powerful tool for pattern matching in strings. We can use a regular expression pattern to check if a string is a valid decimal number.

Here is a code snippet that demonstrates how to use a regular expression to validate decimal numbers:

function isNumeric(input) {
  return /^d*.?d+$/.test(input);
}

// Example usage
console.log(isNumeric("123.45")); // true
console.log(isNumeric("123")); // true
console.log(isNumeric("abc")); // false
console.log(isNumeric("12.34.56")); // false

The regular expression /^d*.?d+$/ checks if the input string consists of zero or more digits followed by an optional decimal point and one or more digits.

Using the isNaN() Function

The isNaN() function in JavaScript is used to check if a value is NaN (Not a Number). We can utilize this function to check if a string is a valid decimal number.

Here is a code snippet that demonstrates how to use the isNaN() function to validate decimal numbers:

function isNumeric(input) {
  return !isNaN(parseFloat(input)) && isFinite(input);
}

// Example usage
console.log(isNumeric("123.45")); // true
console.log(isNumeric("123")); // true
console.log(isNumeric("abc")); // false
console.log(isNumeric("12.34.56")); // false

The parseFloat() function is used to convert the input string to a floating-point number. If the conversion is successful and the input is a finite number, the function returns true. Otherwise, it returns false.

Both approaches discussed above can be used to validate decimal numbers in JavaScript. Choose the one that best suits your needs and the requirements of your project.