Validate Decimal Numbers In Javascript - IsNumeric()

In this article, we'll explore a practical JavaScript method called IsNumeric() to validate decimal numbers.

Whether you're building a form validation system or working on a financial application, ensuring that user inputs are valid numeric values is essential.

How to validate decimal number using Regular Expressions

In this section, we'll discuss how to validate decimal numbers in JavaScript using regular expressions. Regular expressions are a powerful tool for pattern matching and validation.

<script>
  function isNumeric(input) {
    return input +' = '+ /^-?\d\.?\d+$/.test(input);
  }
 console.log(isNumeric('-1'))
 console.log(isNumeric('-1.5'))
 console.log(isNumeric('0'))
 console.log(isNumeric('.42'))
 console.log(isNumeric('99,999'))
 console.log(isNumeric('0x89f'))
 console.log(sNumeric('#abcdef'))
 console.log(isNumeric(''))   
</script>

Explanation of above example:

1. The regular expression /^-?\d\.?\d+$/ matches strings that start with an optional minus sign, followed by zero or more digits, an optional decimal point, and one or more digits.
2. The .test(input) method checks if the input string matches this pattern and returns a Boolean value.

Validate Decimal Numbers Using isNaN() Function

In this section, we'll explore an alternative method to validate decimal numbers using the isNaN() function, which checks for invalid numbers.

<script>
 function isNumeric(input) {
  return !isNaN(parseFloat(input)) && isFinite(input);
 }
 console.log(isNumeric('-1'))
 console.log(isNumeric('-1.5'))
 console.log(isNumeric('0'))
 console.log(isNumeric('.42'))
 console.log(isNumeric('99,999'))
 console.log(isNumeric('0x89f'))
 console.log(sNumeric('#abcdef'))
 console.log(isNumeric(''))   
</script>

Explanation:

1. parseFloat(input) attempts to parse the input string as a floating-point number.
2. isNaN() checks if the result is not a valid number, and isFinite() ensures the number is finite.

Conclusion:

In this article, we explored two methods to validate decimal numbers in JavaScript: using regular expressions and the isNaN() function.