Regular Expression to reformat a US phone number in Javascript

Question

I\'m looking to reformat (replace, not validate - there are many references for validating) a phone number for display in Javascript. Here\'s an example of some of the data:

Answer 1

I'm using this function to format US numbers.

function formatUsPhone(phone) {

    var phoneTest = new RegExp(/^((\+1)|1)? ?\(?(\d{3})\)?[ .-]?(\d{3})[ .-]?(\d{4})( ?(ext\.? ?|x)(\d*))?$/);

    phone = phone.trim();
    var results = phoneTest.exec(phone);
    if (results !== null && results.length > 8) {

        return "(" + results[3] + ") " + results[4] + "-" + results[5] + (typeof results[8] !== "undefined" ? " x" + results[8] : "");

    }
    else {
         return phone;
    }
}

It accepts almost all imaginable ways of writing a US phone number. The result is formatted to a standard form of (987) 654-3210 x123