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Number validation in JavaScript

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Sometimes the data entered into a text field needs to be in the right format and must be of a particular type in order to effectively use the form. For instance, Phone number, Roll number, etc are some details that must be in digits not in alphabet.

Approach: We have used isNaN() function for validation of the text field for numeric value only. Text-field data is passed in the function and if passed data is a number then isNan() returns true and if data is not a number or a combination of both number and alphabets then it returns false.

Below is a code in HTML and JavaScript to validate a text field if it contains a digit or not.

Example:

HTML




<!DOCTYPE html>
<html lang="en">
<head>
    <title>
        Number validation in JavaScript
    </title>
    <script>
        /* this function is called when we
              click on the submit button*/
        function numberValidation() {
            event.preventDefault();
            let n = document.form.numbers.value;
 
            if (isNaN(n)) {
                document.getElementById("numberText")
                    .innerHTML = "Please enter Numeric value";
                return false;
            } else {
                document.getElementById("numberText")
                    .innerHTML = "Numeric value is: " + n;
                return true;
            }
        }
    </script>
</head>
 
<body>
    <img src=
         alt="Avatar"
         style="width: 200px;" />
    <form action="#" name="form" onsubmit="numberValidation()">
        Number: <input type="text" name="numbers" />
        <span id="numberText"></span>
        <br />
        <input type="submit" value="submit" />
    </form>
</body>
</html>

Output: 

 

We have a complete list of Number methods, to check those please go through this JavaScript Number Complete Reference article.


Last Updated : 02 Jun, 2023
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