JavaScript统计字符串中字符出现次数的两种实现方式

<script>
 var ary ="abca12abbc121d";
 
 var obj = {};
 var i = 0;
 ary1 = ary.toLocaleLowerCase(); 
 
 for(i = 0; i < ary1.length; i++)
 {
 key = ary1[i];
 if(obj[key])
 {
 //对象中有这个字母
 obj[key]++;
 }
 else
 {
 //对象中没有这个字母,把字母加到对象中
 obj[key] = 1;
 }
 }
 
 for(var key in obj) //遍历这个对象
 {
 console.log(key + "这个字符出现了" + obj[key] + "次");
 }
</script>

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>Document</title>
 <script src="sc/char-sunmmary.js"></script>
 <script>
 window.onload=function(){
  var txtChars=document.getElementById("txt-chars");
  var show=document.getElementById("show");
  document.getElementById("btn-ok").onclick=function(){
  var str=txtChars.value;
  var charTotal=total(str);
  // 降序
  charTotal.sort(function(a,b){
   return (a.count-b.count)*-1;
  })
  
  show.innerHTML="<ul>";
  //slice(0,5)取前五
  for(var ct of charTotal.slice(0,5)){
   show.innerHTML+="<li>"+ct.char+"出现了"+ct.count+"次</li>";
  }
  show.innerHTML+="</ul>";
  }
 }
 </script>
</head>
<body>
 <label for="txt-chars">请输入一串字符：</label>
 <input type="text" id="txt-chars" name=""/>
 <button id="btn-ok">确定</button>
 <p id="show"></p>
</body>
</html>

function Summary(char,count) {
 this.char=char;
 this.count=count;
}
// 传递字符串，返回出现频率
function total(str) {
 var result=[];
 for(var c of str){
 var charObj=checkChar(result,c);
 if(charObj==null){
  result.push(new Summary(c,1));
 }
 else{
  charObj.count++;
 }
 }
 return result;
}
// 在数组arr中查找包含字符char的summary实列
//如果存在，则返回该实例，否则返回null
function checkChar(arr,char) {
 var r=null;
 for(var c of arr){
 if(c.char==char){
  r=c;
  break;
 }
 }
 return r;
}