Write a program that inserts parentheses, a space, and a dash into a string of 10 user-entered numbers to format it as a phone number. for example, 5153458912 becomes (515) 345-8912. if the user does not enter exactly 10 digits, display an error message. continue to accept user input until the user enters 999.

const readline = require('readline-sync');

let reg = /^(\d{3})(\d{3})(\d{4})$/;

do {

let number = readline.question("Enter a phone number: ");

if (number === '999') {

 process.exit();

}

var r = number.match(reg);

if (!r) console.log("That is not right.");

else {

 console.log(`(${r[1]}) ${r[2]}-${r[3]}`);

}

} while (true);

Explanation:

This is a javascript solution using regular expressions.

answervpn;