How to get the query string by javascript?

You can easily build a dictionary style collection…

function getQueryStrings() { 
  var assoc  = {};
  var decode = function (s) { return decodeURIComponent(s.replace(/\+/g, " ")); };
  var queryString = location.search.substring(1); 
  var keyValues = queryString.split('&'); 

  for(var i in keyValues) { 
    var key = keyValues[i].split('=');
    if (key.length > 1) {
      assoc[decode(key[0])] = decode(key[1]);
    }
  } 

  return assoc; 
} 

And use it like this…

var qs = getQueryStrings();
var myParam = qs["myParam"];