turns query params into key:value pairs

getParams.js

/**
 * returns an object with all query parameters as key/value pairs
 * @param payload - if ommitted, returns all params as an object; if passed as string specifying a parameter,
 *   returns the value of the specified parameter name; can be passed as object { search: document.location.search, returnKey: {{parameter-name}} }
 * @returns {object} - example: http://example.com?a=a-value&B=B-VALUE = > { "a": "a-value", "b": "B-VALUE"}
 */
function getParams(payload) {
  var searchString = document.location.search,
    returnKey = "";

  if (typeof (payload) === "string") {
    returnKey = payload;
  } else {
    payload = payload || {};
    searchString = payload.search || searchString;
    returnKey = payload.returnKey || returnKey;
  }

  if (searchString) {
    searchString = searchString;
    searchString = /\?/.test(searchString) ? searchString.split('?')[1] : searchString;
    searchString = searchString.split("&");

    if (searchString.length > 0) {
      var output = {};
      for (var i = 0, max = searchString.length; i < max; i++) {
        var tmp = searchString[i].split("=");
        output[tmp[0].toLowerCase()] = decodeURIComponent(tmp[1]);
      }
      return (returnKey) ? output[returnKey] : output;
    }
  } else {
    return (returnKey) ? "" : {};
  }
}