Flatten a JavaScript Object into a Flat Object With Dot Notation Prop Names

gistfile1.js

function flatten(obj,prefix){

            var propName = (prefix) ? prefix + '.' :  '',
                ret = {};

            for(var attr in obj){
                
                if(_.isArray(obj[attr])){
                    var len = obj[attr].length;
                    ret[attr] = obj[attr].join(',');
                }
                else if(typeof obj[attr] === 'object'){
                    _.extend(ret,flatten(obj[attr], propName + attr));
                }
                else{
                    ret[propName + attr] = obj[attr];
                }
            }
  return ret;

}

Example: http://jsfiddle.net/bittersweetryan/5w5qQ/