I need to get all the cookies from the browser

You can only access cookies for a specific site. Using document.cookie you will get a list of escaped key=value pairs seperated by a semicolon.

secret=do%20not%20tell%you;last_visit=1225445171794

To simplify the access, you have to parse the string and unescape all entries:

var getCookies = function(){
  var pairs = document.cookie.split(";");
  var cookies = {};
  for (var i=0; i<pairs.length; i++){
    var pair = pairs[i].split("=");
    cookies[(pair[0]+'').trim()] = unescape(pair.slice(1).join('='));
  }
  return cookies;
}

So you might later write:

var myCookies = getCookies();
alert(myCookies.secret); // "do not tell you"