How can I implement custom validation in JavaScript?

How can I implement custom validation in JavaScript?

You can create custom validation by using JavaScript functions to check user input against specific criteria. Would you like an example?

Yes, please provide an example of custom validation for an email input.

Sure! You can use a regular expression to validate an email. Here's a simple function:

function validateEmail(email) {
    const regex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
    return regex.test(email);
}

This function returns true if the email is valid.

What if I want to show an error message when the validation fails?

You can modify the function to return an error message. For example:

function validateEmail(email) {
    const regex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
    if (!regex.test(email)) {
        return 'Invalid email format!';
    }
    return 'Valid email!';
}