The $.param( ) inverse function in JavaScript / jQuery

Solution 1:

You should use jQuery BBQ's deparam function. It's well-tested and documented.

Solution 2:

This is a slightly modified version of a function I wrote a while ago to do something similar.

var QueryStringToHash = function QueryStringToHash  (query) {
  var query_string = {};
  var vars = query.split("&");
  for (var i=0;i<vars.length;i++) {
    var pair = vars[i].split("=");
    pair[0] = decodeURIComponent(pair[0]);
    pair[1] = decodeURIComponent(pair[1]);
        // If first entry with this name
    if (typeof query_string[pair[0]] === "undefined") {
      query_string[pair[0]] = pair[1];
        // If second entry with this name
    } else if (typeof query_string[pair[0]] === "string") {
      var arr = [ query_string[pair[0]], pair[1] ];
      query_string[pair[0]] = arr;
        // If third or later entry with this name
    } else {
      query_string[pair[0]].push(pair[1]);
    }
  } 
  return query_string;
};