Accessing cookies of an iFrame in parent window

Question

I am loading an iFrame of a different domain. Both the parent and the iFrame sites are under my control. I'm using iFrame.postMessage to post messages to the iFrame. The site which I'm loading through the iFrame has a cookie(not a http only cookie). I need to read this cookie inside the parent site.

   var opIFrame=document.getElementById('opIFrame').contentWindow;

    /**
 * periodically invoking the Endpoint at OP for every six seconds
 */
setInterval(function(){
    console.log('Sending polling Request From RP Client ... ' + clientId);
    document.all.opIFrame.src = endPoint;
    opIFrame.postMessage(clientId,"https://localhost:9443/oauth2/loginstatus");
    var session=getCookieValue("session_state");
    console.log('**session**'+session);
},6000);


function getCookieValue(cookieName) {
var name = cookieName + "=";
var cookies =document.cookie.split(';');
if (!cookies) {
    return null;
}
for (var i = 0; i < cookies.length; i++) {
    var cookie = cookies[i].trim();
    if (cookie.indexOf(name) == 0) {
        return cookie.substring(name.length, cookie.length);
    }
}
return null;

}

I used the above methods to read the cookie. But it was not successful. Please advice me on this.

Updated Code:

<iframe id="opIFrame" style='visibility: hidden;' src=endpoint onload="getCookieValue('session_state')" >
</iframe> 
   <script>function getCookieValue(cookieName) {
        console.log("=====getCookieValue=======");
        var cookies = document.cookie;
        console.log("=====ALL cookies======="+cookies);
    }</script>

I'm getting empty array for cookies though I Can see the cookie in my browser.

Answer 1

This will give you the cookie of the iframe:

var cookie = document.getElementById("iframeId").contentDocument.cookie;

To get a cookie by name use this function (from stackoverflow):

function getCookie(cookie, name) {
    function escape(s) { return s.replace(/([.*+?\^${}()|\[\]\/\\])/g, '\\$1'); };
    var match = cookie.match(RegExp('(?:^|;\\s*)' + escape(name) + '=([^;]*)'));
    return match ? match[1] : null;
}