Od pole k objektům

Začněme úlohou: 

<!DOCTYPE html>
<html lang="cs">
<head>
    <meta charset="utf-8" />
    <title>Titulek</title>
 
    <style>
    /* Vychozi CSS stylovani prijde sem*/
 
 
 
    /* */
    </style>
 
</head>
 
<body>
 <div id="vystup"></div>
    <script>
    /* <![CDATA[ */
var tramvaje = [15, 20, 12, 20]
var nalezeno = 0
for(var i=0;i<tramvaje.length;i++){
 //vykona se pro kazdy prvek
 if(tramvaje[i] == '20'){
  nalezeno++
 }
}
document.getElementById('vystup').innerHTML = nalezeno
 
    /* ]]> */
    </script>
</body>
</html>
<!DOCTYPE html>
<html lang="cs">
<head>
    <meta charset="utf-8" />
    <title>Titulek</title>
 
    <style>
    /* Vychozi CSS stylovani prijde sem*/
 	td {border: 1px solid black; padding:0.3em}
 	table {border-collapse: collapse}
 
 
    /* */
    </style>
 
</head>
 
<body>
 <table id="vystup"><tr><th>Tramvaj</th><th>Pozorování</th></tr></table>
    <script>
    /* <![CDATA[ */
    var tramvaje = [15, 20, 12, 20, 15, 7, 15, 20, 7, 7, 7]
 
 // Ukol 2
 // pocet pozorovani tramvaje 20, 15, 7  
 // Ukol 3
 // naleznete tramvaj s nejvice pozorovanimi
var maximalniHodnota = 0
var tramvajSMaximalniHodnotou = 0
for(var cilovaTramvaj = 1; cilovaTramvaj < 40; cilovaTramvaj++){
	var nalezeno = 0
	for(var i=0;i<tramvaje.length;i++){
	 //vykona se pro kazdy prvek
	 if(tramvaje[i] == cilovaTramvaj){
	  nalezeno++
	 }
	}
	if(nalezeno > maximalniHodnota){
	maximalniHodnota = nalezeno
	tramvajSMaximalniHodnotou = cilovaTramvaj
	}
	// "nalezeno" je pocet pozorovani tramvaje "cilovaTramvaj"
	document.getElementById('vystup').innerHTML+= "<tr><td>"+cilovaTramvaj+"</td><td>"+nalezeno+"</td></tr>" 
}
//document.getElementById('vystup').innerHTML = tramvajSMaximalniHodnotou+":"+maximalniHodnota
 
 
 
    /* ]]> */
    </script>
</body>
</html>

S polem

<!DOCTYPE html>
<html lang="cs">
<head>
    <meta charset="utf-8" />
    <title>Titulek</title>
 
    <style>
    /* Vychozi CSS stylovani prijde sem*/
 	td {border: 1px solid black; padding:0.3em}
 	table {border-collapse: collapse}
 
 
    /* */
    </style>
 
</head>
 
<body>
 <table id="vystup"><tr><th>Tramvaj</th><th>Pozorování</th></tr></table>
    <script>
    /* <![CDATA[ */
    tramvaje = [15, 20, 12, 20, 15, 7, 15, 20, 7, 7, 7]
 
    var pocetVyskytuTramvaje = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    for(var i = 0; i < tramvaje.length; i++){
        var cisloTramvaje = tramvaje[i]
        pocetVyskytuTramvaje[cisloTramvaje]++
    }
 
    // Vypsat kolikrat projela konkretni tramvaj
    console.log("Dvacitka projela: " + pocetVyskytuTramvaje[20])
 
    // Najit maximum ... ?
 
 
    /* ]]> */
    </script>
</body>
</html>