Counts the number of occurrences of each character in the string

Count the number of occurrences of each character in the string

subject ：
Count the number of times each character appears in a string , And return the letter with the most occurrences and the corresponding number of times

answer ：
utilize reduce function , Think of each character as an empty box , After traversing, the value is transferred to the empty box , Finally, determine how much is in the empty box

var str="helloworld";
var arr=str.split("");
var result=arr.reduce(
    function(prev,elem){
    
// When you get to this number, add... To this number 1 Time 
        if(prev[elem]===undefined){
    
            prev[elem]=1;
        }else{
    
            prev[elem]+=1;
        }
        return prev;
    },
    {
    }
)
var char,count;
// Traverse result Each member in 
for(var key in result){
    
// The first time, if not 
    if(char===undefined){
    
        char=key;
        count=result[key];
    }else{
    
        // otherwise , Start making comparisons 
        if(result[key]>count){
    
            char=key;
            count=result[key];
        }
    }
}
console.log(`${
      char} The most frequent occurrence , Altogether ${
      count} Time `);

function strNum(str){
    
            let obj = {
    };
            for(let i=0;i<str.length;i++){
    
                let value = str.charAt(i)
                if(obj[value]){
    
                    obj[value]++
                }else{
    
                    obj[value] = 1
                }
            }
            let word = null
            let temp = 0
            for(let key in obj){
    
                if(obj[key]>temp){
    
                    temp = obj[key]
                    word = key
                }
            }
            return [word, temp].join(' ')
        }
        console.log(strNum('helloword'));

return Return multiple values

1. return {a,b,c}
2. return [a,b,c]

Knowledge point ：reduce()、 loop