below is a snippet of code that I started with... then I made some changes based on the commented suggestion from stackoverflow user. (Please see below for my progress so far)

ORIGINAL

$valid = true;

    // basic validation
    $phoneNumber = str_replace( ' ', '', $phoneNumber );
    if ( strlen( $phoneNumber ) < 10 || !is_numeric( $phoneNumber ) ) {
        $valid = false;
    }

    $areaCode  = substr($phoneNumber, 0, 3);
    $prefix    = substr($phoneNumber, 3, 3);
    $mainPhone = substr($phoneNumber, 3, 7);

    // perform the same regex matching:
    if ($valid) {
        $regex = '/^(?:\([2-9]\d{2}\)\ ?|[2-9]\d{2}(?:\-?|\ ?))/';
        $valid = preg_match($regex, $areaCode);
    }
    if ($valid) {
        $regex = '/^(?!\d[1]{2}|[5]{3})([2-9]\d{2})([. -]*)\d{4}$/';
        $valid = preg_match($regex, $mainPhone);
    }

    // perform the original web validation:
    if ( $valid ) {
        // validate area code
        if ( 
             $areaCode == '000' ||
             $areaCode == '111' ||
             $areaCode == '222' ||
             $areaCode == '333' ||
             $areaCode == '444' ||
             $areaCode == '555' ||
             $areaCode == '666' ||
             $areaCode == '777' ||
             $areaCode == '999' ||
             $areaCode == '123' || (is_string($areaCode) && !is_numeric($areaCode))) {
            $valid = false;
        }
    }

    if ( $valid ) {
        // validate prefix
        if ( $prefix == '123' ||
             $prefix == '000' ||
             $prefix == '111' ||
             $prefix == '555' || (is_string($prefix) && !is_numeric($prefix))) {
            $valid = false;
        }
    }

    if ( $valid ) {
        // validate main phone number

        if ( $mainPhone == '2222222' ||
             $mainPhone == '3333333' ||
             $mainPhone == '4444444' ||
             $mainPhone == '6666666' ||
             $mainPhone == '7777777' ||
             $mainPhone == '8888888' ||
             $mainPhone == '9999999' || (is_string($phoneNumber) && !is_numeric($phoneNumber))) {
            $valid = false;
        }
    }

    return $valid;

NEW JAVASCRIPT VERSION (SO FAR)

below is a snippet of code that I am converting so far... I still have some PHP stuff in there can you guys help me out to remove/replace what this snippet needs to say to make it work?

function is_numeric(n) {
        return !isNaN(parseFloat(n)) && isFinite(n);
    }

function phonenumberIsValid(phonenumber)
{

var valid = true;

    // basic validation
    var phonetest = phonenumber.replace(' ','');
    if ( strlen( phonetest ) < 10 || !is_numeric( phonetest ) ) {
       valid = false;
    }

    var areaCode  = phonetest.substr(0,3);
    var prefix    = phonetest.substr(3,3);
    var mainPhone = phonetest.substr(3,7);


    // perform the same regex matching that LeadMaster does:
    if(valid){
        valid = areaCode.match('/^(?:\([2-9]\d{2}\)\ ?|[2-9]\d{2}(?:\-?|\ ?))/');
    }

    if(valid){
        valid = mainPhone.match('/^(?!\d[1]{2}|[5]{3})([2-9]\d{2})([. -]*)\d{4}$/');
    }

    // perform the original web validation:
    if(valid){
        // validate area code
        if ( 
             areaCode == '000' ||
             areaCode == '111' ||
             areaCode == '222' ||
             areaCode == '333' ||
             areaCode == '444' ||
             areaCode == '555' ||
             areaCode == '666' ||
             areaCode == '777' ||
             areaCode == '999' ||
             areaCode == '123' || (!is_numeric(areaCode)) {
             valid = false;
        }
    }

    if(valid) {
        // validate prefix
        if ( prefix == '123' ||
             prefix == '000' ||
             prefix == '111' ||
             prefix == '555' || (!is_numeric(prefix)) {
             valid = false;
        }
    }

    if(valid) {
        // validate main phone number

        if ( mainPhone == '2222222' ||
             mainPhone == '3333333' ||
             mainPhone == '4444444' ||
             mainPhone == '6666666' ||
             mainPhone == '7777777' ||
             mainPhone == '8888888' ||
             mainPhone == '9999999' || (!is_numeric(phoneNumber)) {
             valid = false;
        }
    }

    return valid;

}