Parse Url Param by Vanilla JavaScript

GetUrlParameter.js

function getUrlParameter(sParam) {
  var sPageURL = decodeURIComponent(window.location.search.substring(1)),
      sURLVariables = sPageURL.split('&'),
      sParameterName

  for (var i = 0; i < sURLVariables.length; i++) {
    sParameterName = sURLVariables[i].split('=')
    if (sParameterName[0] === sParam) {
        return sParameterName[1] === undefined ? true : sParameterName[1]
    }
  }
}