Retrieve HTTP Get parameter from URL

gistfile1.js

/**
 * Parse URL and retrieve a GET parameter
 *
 * @param   variable  Name of variable to retrieve from URL
 * @returns           Value of the variable or null if not present
 *
 * from: http://stackoverflow.com/questions/827368/use-the-get-paramater-of-the-url-in-javascript
 */
function getQueryVariable(variable) {
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  for (var i=0;i<vars.length;i++) {
    var pair = vars[i].split("=");
    if (pair[0] == variable) {
      return pair[1];
    }
  } 
  return null;
}