var isset = function(myVarString){

    var arr = myVarString.split("."); //get properties - only works with "<property>.<property>" notation.
    var last = "this.";
    for(var i = 0; i < arr.length; i++){
        if(typeof eval(last + arr[i]) !== "undefined"){
           last = last + arr[i] + ".";
        } else {
        	return false;
        }
    }

    return true;

};

/*
* - Usage
*
*

if(isset('objectName.childProperty.grandchildProperty')){
  //do stuff
}

*/