// removes the leading and trailing spaces from a string,
// similar to the java.lang.String.trim() function
// taken from http://www.salesforce.com
function trim(st) {
    var len = st.length
    var begin = 0, end = len - 1;
    while (st.charAt(begin) == " " && begin < len) {
        begin++;
    }
    while (st.charAt(end) == " " && begin < end) {
        end--;
    }
    return st.substring(begin, end+1);
}


function formatPhone (field) {
    field.value = trim(field.value);

    var ov = field.value;
    var v = "";
    var x = -1;

    // is this phone number 'escaped' by a leading plus?
    if (0 < ov.length && '+' != ov.charAt(0)) { // format it
        // count number of digits
        var n = 0;
        if ('1' == ov.charAt(0)) {  // skip it
            ov = ov.substring(1, ov.length);
        }
        
        for (i = 0; i < ov.length; i++) {
            var ch = ov.charAt(i);

            // build up formatted number
            if (ch >= '0' && ch <= '9') {
                if (n == 0) v += "(";
                else if (n == 3) v += ") ";
                else if (n == 6) v += "-";
                v += ch;
                n++;
            }
            // check for extension type section;
            // are spaces, dots, dashes and parentheses the only valid non-digits in a phone number?
            if (! (ch >= '0' && ch <= '9') && ch != ' ' && ch != '-' && ch != '.' && ch != '(' && ch != ')') {
                x = i;
                break;
            }
        }
        // add the extension
        if (x >= 0) v += " " + ov.substring(x, ov.length);

        // if we recognize the number, then format it
        if (n == 10 && v.length <= 40) field.value = v;
    }
    return true;
}