URL Query parameter helpers: 1. on-demand access function `getParam` 2. onpopstate object creation of `window.location.params`

queryParams.js

// Inspired by http://stackoverflow.com/questions/901115/how-can-i-get-query-string-values-in-javascript
;(function() {
  'use strict';

  // On-demand retreival of query params
  window.getParam = function getParam(name) {
    var rxName = new RegExp('[\\?&]'+name+'[=]([^&#]*)');
    var check = rxName.exec(window.location.search);
    return (check === null) ? check : decodeURIComponent(check[1].replace(/\+/g, ' '));
  };

  // Run-once params object setup (on history change)
  // window.location.params
  ;(window.onpopstate = function() {
    var rxParams = /([^\?&=]+)=?([^&#]*)/g;
    var decode = function decode(s) { return decodeURIComponent(s.replace(/\+/g, " ")); };
    var match;

    window.location.params = {};
    while (match = rxParams.exec(window.location.search)) {
      window.location.params[decode(match[1])] = decode(match[2]);
    }
  }());
}());