CODE EXAMPLE FOR JAVASCRIPT

javascript Validating the Phone Number

// program to validate the phone number
function validatePhone(num) {
    // regex pattern for phone number
    const re = /^(?([0-9]{3}))?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$/g;
    // check if the phone number is valid
    let result = num.match(re);
    if (result) {
        console.log('The number is valid.');
    }
    else {
        let num = prompt('Enter number in XXX-XXX-XXXX format:');
        validatePhone(num);
    }
}

// take input
let number = prompt('Enter a number XXX-XXX-XXXX');

validatePhone(number);