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Explain explicity what function does

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I tried program these functions and i thought i knew what they did, but apparently i don't. First it tries grab midi object and returns success and failure that much i get.

var output;var input;var inputs;var outputs;var mid; var onMIDIMessage; var message;

if (navigator.requestMIDIAccess) {
    navigator.requestMIDIAccess()
        .then(success, failure);
}

function failure () {
    console.error('No access to your midi devices.'+ + msg )
}

function success (midi) {
    mid=midi;
    inputs = mid.inputs.values();
    console.log("Undefined value?="+inputs[0]);
    // inputs outputs are Iterators
    for (input = inputs.next(); input && !input.done; input = inputs.next()) {
       // each time there is a midi message call the onMIDIMessage function?
       input.value.onmidimessage = onMIDIMessage;
    } 
}


So I thought above success function grabbed The midi object whatever that is listened to incomingmessages on the last port because "next". 
So it is basicly some sort of port listener, well it seem weird to me, but who am i to judge?

And that below function listed outputs ports in portout "object array?" and input ports in portin "object array?"

function selectPorts(){
   portout = mid.outputs.values();
   portin = mid.inputs.values();

   for (input = portin.next(); input && !input.done; input = portin.next()) {
           var deviceIn = input.value.name;
           var optin = document.createElement("option");
           optin.text = deviceIn;
           document.getElementById("in_portsel").add(optin);
  } 
   
   for (output = portout.next(); output && !output.done; output = portout.next()) {
       var deviceOut = output.value.name;
       //console.log(deviceOut);
       var optout = document.createElement("option");
       optout.text = deviceOut;
       document.getElementById("out_portsel").add(optout);
   }
}

So I thought it scrolled thru input ports and output ports added them to an option list. And i thought that the "input" would be the last one scrolled thru and the output would be the last scrolled thru. And i could read midimessages from that  input and echo them to that output. 

Because so it seemed on win XP, not so much on win 7,8 and 10.

function onMIDIMessage (message) {
     playbackPort(message); 
}

Don't ask me how message get a value above because i am baffeled myself...

function playbackPort(message){
 var noteMessage = [message.data[0], message.data[1], message.data[2]];
 output.send(noteMessage); 
} 

So can anyone explain "what i try to do" and "what i fail todo"?
I really would like to make my rudimentary sequenser, but since i do not understand the logic of ports above i am stuck in undefined land when i try.

output.send(noteMessage) undefined...

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Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 14:52 -0700
  Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 15:11 -0700
    Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 15:16 -0700
      Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 16:00 -0700
        Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 16:03 -0700
  Re: Explain explicity what function does JJ <jj4public@vfemail.net> - 2018-08-16 06:47 +0700
    Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 21:43 -0700
      Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 23:13 -0700
        Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 23:18 -0700
          Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 23:23 -0700
    Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 23:44 -0700
      Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-15 23:49 -0700
        Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-16 01:26 -0700
          Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-17 01:49 -0700
            Re: Explain explicity what function does Flng Fck <nothanks@invalid.invalid> - 2018-08-17 16:02 +0200
              Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-17 11:29 -0700
                Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-17 11:33 -0700
                Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-17 11:36 -0700
              Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-19 11:22 -0700
                Re: Explain explicity what function does "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2018-08-19 22:52 +0200
                Re: Explain explicity what function does Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-08-20 00:15 +0200
                Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-19 15:21 -0700
                Re: Explain explicity what function does Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-08-20 00:27 +0200
                Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-19 15:43 -0700
                Re: Explain explicity what function does Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-08-19 15:48 -0700

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