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 jа vascript solution using regular expressions.