Format a phone number

formatphone.js

/*
	Formats a typical US phone number, including an extension (if preceeded by something like x, ex, ext, etc).
	Crude but adequate.
*/

String.prototype.formatPhone = function () {
    
    var phone = this;

    if (!phone) return "";

    var ex;
    var ph = phone;
    var exidx = ph.search(/[e|x]/);

    if (exidx >= 0) {
        ex = ph.substring(exidx).replace(/\D/g, '');
        ph = ph.substring(0, exidx);
    }

    ph = ph.replace(/\D/g, '');

    if (ph.indexOf('1') == 0) ph = ph.substring(1);

    if (ph.length != 10) return phone;

    ph = ph.substring(0, 3) + '-' + ph.substring(3, 6) + '-' + ph.substring(6);

    if (ex) ph += " x" + ex;

    return ph;

}