Checking the Current Logged User Group using ECMA Script

var strCheckLoggedUser="";
var strCurrentUserName="";

function CheckAdminGroup()
{
    var currentContext = new SP.ClientContext();
    strCurrentUserName= currentContext.get_web().get_currentUser();
    currentContext.load(strCurrentUserName);
   
    var groupCollection = currentContext.get_web().get_siteGroups();
    var _group = groupCollection.getById(3);
    //Note:- Here 3 is the Admin Group ID.
   
    strCheckLoggedUser= _group.get_users();
    currentContext.load(strCheckLoggedUser);
    currentContext.executeQueryAsync(Function.createDelegate(this, this.UserAvailableinAdminGroup), Function.createDelegate(this, this.UserNotAvailableinAdminGroup));
}

function UserAvailableinAdminGroup()
{
    debugger;
    var strValidUser=false;
    var listEnumerator = strCheckLoggedUser.getEnumerator();
    while (listEnumerator.moveNext())
    {
        var item = listEnumerator.get_current();
        if (strCurrentUserName.get_loginName() == item.get_loginName())
        {
            strValidUser=true;
            break;
        }
    }
   
    if(strValidUser==true)
    {
        //Write your Functionality what u want to perform if the user logged in is a Admin User
        alert('Logged in user is Admin User');
    }
}

function UserNotAvailableinAdminGroup()
{
   
}

ExecuteOrDelayUntilScriptLoaded(CheckAdminGroup, "sp.js");