h5 js判断是IOS系统还是android系统

function detect(){
  var equipmentType = "";
  var agent = navigator.userAgent.toLowerCase();
  var android = agent.indexOf("android");
  var iphone = agent.indexOf("iphone");
  var ipad = agent.indexOf("ipad");
    if(android != -1){
        equipmentType = "android";
    }
    if(iphone != -1 || ipad != -1){
      equipmentType = "ios";
    }
      return equipmentType;
     }