JS1k: The JavaScript code golfing competition

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/**
 *  @title "COIN COIN SCORE" by Patrice CHASSAING
 *  @js1ktitle "COIN COIN SCORE" by Patrice CHASSAING
 *  @description Create a musical score. Use select options to add musical notes. "_" means a silence. "END" will stop the song, even if there are notes remaining. Use Play and Stop buttons...
 *  @file javascript into shim.html
 *  @version 2018-02-25-11-55-00
 *  @date 2018/02/25
 *  @author Patrice CHASSAING
 *  @running Firefox ESR 52.6.0, running on Debian 8.10
 *  @running Chromium 57.0.2987.98 Built on 8.7, running on Debian 8.10
 *  @copyright Me
 *  @brief JS1k 2018 demo contest
 *  @compressedsize 1021 Bytes
 */
//Declaration
var d = document
	, II;//Timer variables

// getElementById function
function g(U) { return d.getElementById(U) }

/* MAIN */

//Set up the scene
b.innerHTML = '<style>*{font-size:20px;height:40px}select{width:80px}</style><div id="S"></div>';

S=g('S');
//Here a good page that associates notes and frequencies : http://jeanjacques.dialo.free.fr/frequenc.htm
var _nF = 	['', '_', 'Do',   'Réb',   'Ré',  'Mib', 'Mi', 'Fa', 'Solb', 'Sol', 'Lab',   'La', 'Sib', 'Si', 'Do', 'END']//Notes - Could be ABC notation ...
  , _f = 	[ 0,  0,  262,     277,    294,    311,  330,  349,   370,   392,    415,    440,   466,  494,  523,     -1]//Notes frequencies Hz
  , _p =	[];//Musical score
nms = 400; 	//play note milliseconds
ns = nms/1000;	//play note seconds
nn = 0;//Notes n°

	function N(selectedIndex){
		n='';
		nn+=1
		for (var i = 0; i < _nF.length; i++) {
		//if (selectedIndex==_nE[i]) {sel='selected'} else {sel=''};//'+sel+' 
  		n=n+'<option value="'+_f[i]+'">'+_nF[i]+'</option>';//+' '+_nE[i]
  		}
		n='<select id="'+nn+'" onchange="N()">'+n+'</select>';
		S.insertAdjacentHTML('beforeend', n);
		}

n='<input id="PP" type="button" value="Play" onclick="PPlay()"/><input id="PS" type="button" value="Stop" onclick="PStop()"/><div id="F"></div>';
S.insertAdjacentHTML('beforebegin', n);
	
	N();
	
			// create web audio api context
			var aC = new (window.AudioContext || window.webkitAudioContext)();
	
	function PN(f){		
			// create Oscillator node
			var o = aC.createOscillator();
			o.type = 'square';	
			o.frequency.value=f;
			o.connect(aC.destination);
			o.start();
			o.stop(aC.currentTime+ns);
		}
	
	function PP(){	
			var e = g(ni);			
			f = e.options[e.selectedIndex].value;	// value in hertz
			n = e.options[e.selectedIndex].text;	// note value
			if (f!=-1 && ni<nn){
				_p.push(n);
				PN(f);				
				ni=ni+1;
				}
			else {PStop();g('F').innerHTML= _p.join(',')}
			}
	
	function PPlay(){
			_p = [];
			g('PP').disabled=true;
			ni=1;
			II = setInterval(PP, nms);
			}

	function PStop(){g('PP').removeAttribute("disabled");clearInterval(II);}

	//That's all...