Count number of occurrences for each char in a string

Question

I want to count the number of occurrences of each character in a given string using JavaScript.

For example:

var str = \"I want to count the number         


        

Answer 1

You can use the maps in ES6 in Javascript. Provides a cleaner and concise code in my opinion. Here is how I would go about

function countChrOccurence ('hello') {
 let charMap = new Map();
 const count = 0;
  for (const key of str) {
   charMap.set(key,count); // initialize every character with 0. this would make charMap to be 'h'=> 0, 'e' => 0, 'l' => 0, 
  }

  for (const key of str) {
    let count = charMap.get(key);
    charMap.set(key, count + 1);
  }
// 'h' => 1, 'e' => 1, 'l' => 2, 'o' => 1

  for (const [key,value] of charMap) {
    console.log(key,value);
  }
// ['h',1],['e',1],['l',2],['o',1]
}  

Answer 2

Hope this helps someone

function getNoOfOccurences(str){
    var temp = {};
    for(var oindex=0;oindex<str.length;oindex++){
        if(typeof temp[str.charAt(oindex)] == 'undefined'){
            temp[str.charAt(oindex)] = 1;
        }else{
            temp[str.charAt(oindex)] = temp[str.charAt(oindex)]+1;
        }
    }
    return temp;
}

Answer 3

 // Converts String To Array
        var SampleString= Array.from("saleem");

        // return Distinct count as a object
        var allcount = _.countBy(SampleString, function (num) {
            return num;
        });

        // Iterating over object and printing key and value
        _.map(allcount, function(cnt,key){
            console.log(key +":"+cnt);
        });

        // Printing Object
        console.log(allcount);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

    <p>Set the variable to different value and then try...</p>
    

Answer 4

This worked well for me :

    function Char_Count(str1) {
    var chars = {};
    str1.replace(/\S/g, function(l){chars[l] = (isNaN(chars[l]) ? 1 : 
    chars[l] + 1);});
    return chars;
  }

  var myString = "This is my String";
  console.log(Char_Count(myString));

Answer 5

I am giving you very very simple code.

 // Converts String To Array
        var SampleString= Array.from("saleem");

        // return Distinct count as a object
        var allcount = _.countBy(SampleString, function (num) {
            return num;
        });

        // Iterating over object and printing key and value
        _.map(allcount, function(cnt,key){
            console.log(key +":"+cnt);
        });

        // Printing Object
        console.log(allcount);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

    <p>Set the variable to different value and then try...</p>
    

Answer 6

    package com.company;

import java.util.HashMap;


 public class Main {

    public static void main(String[] args) {
    // write your code here
    HashMap<Character, Integer> sHashMap = new HashMap();  // using hashMap<key , value > here key = character and  value = count

    String arr = "HelloWorld";

    for (int i = 0; i < arr.length(); i++) {
        boolean flag = sHashMap.containsKey(arr.charAt(i));  // check if char is already  present 

    if (flag == true)
        {
            int Count = sHashMap.get(arr.charAt(i)); // get the char count
            sHashMap.put(arr.charAt(i), ++Count); //   increment the count and update in hashMap
        } 
        else 
        {
            sHashMap.put(arr.charAt(i), 1); //if  char not present then insert into hashMap
        }
    }

     System.out.println(sHashMap);
    //OutPut would be like ths {r=1, d=1, e=1, W=1, H=1, l=3, o=2}

}

}