function swapImagePng(img) {
    thisSrc = img.src
    if (thisSrc.indexOf("On") > 0) {
        thisSrc = thisSrc.replace("On.png", ".png")
        img.src = thisSrc
    } else {
        thisSrc = thisSrc.replace(".png", "On.png")
        img.src = thisSrc
    }
}

// function: email validation
function isEmailValid(str) {
    var at = "@"
    var dot = "."
    var lat = str.indexOf(at)
    var lstr = str.length
    var ldot = str.indexOf(dot)

    if (str.indexOf(at) == -1) {
        return false
    }
    if (str.indexOf(at) == -1 || str.indexOf(at) == 0 || str.indexOf(at) == lstr) {
        return false
    }
    if (str.indexOf(dot) == -1 || str.indexOf(dot) == 0 || str.indexOf(dot) == lstr) {
        return false
    }
    if (str.indexOf(at, (lat + 1)) != -1) {
        return false
    }
    if (str.substring(lat - 1, lat) == dot || str.substring(lat + 1, lat + 2) == dot) {
        return false
    }
    if (str.indexOf(dot, (lat + 2)) == -1) {
        return false
    }
    if (str.indexOf(" ") != -1) {
        return false
    }
    return true
}

function _isInteger(val) {
    var digits = "1234567890";
    for (var i = 0; i < val.length; i++) {
        if (digits.indexOf(val.charAt(i)) == -1) { return false; }
    }
    return true;
}

function trim(str) {
    return str.replace(/^\s+|\s+$/g, "");
}

// function: check phone number
var digits = "0123456789";
var phoneNumberDelimiters = "()- ";
var validWorldPhoneChars = phoneNumberDelimiters + "+";
var minDigitsInIPhoneNumber = 10;

function stripCharsInBag(s, bag) {
    var i;
    var returnString = "";
    for (i = 0; i < s.length; i++) {
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

function checkPhoneNumber(strPhone) {
    strPhone = trim(strPhone);
    s = stripCharsInBag(strPhone, validWorldPhoneChars);
    return (_isInteger(s) && s.length >= minDigitsInIPhoneNumber);
}



// function: force enter click
function forceClick(e, elemId) {
    var elem = document.getElementById(elemId);
    var evt = (e) ? e : window.event;
    var intKey = (evt.which) ? evt.which : evt.keyCode;

    if (intKey == 13) {
        elem.click();
        return false;
    }
    return true;
}