How to write a javascript code that counts each character occurrence in a string ?

e.g 
String is : Hello World 

Output :  
count of H -> 1
count of e -> 1
count of l -> 3
count of o -> 2 
count of r -> 1
count of d -> 1 
count of W -> 1 

How to write a javascript code that counts each character occurrence in a string ?

e.g 
String is : Hello World 

Output :  
count of H -> 1
count of e -> 1
count of l -> 3
count of o -> 2 
count of r -> 1
count of d -> 1 
count of W -> 1 

• javascript

• i tried split, match but it didnt work ... – Vikash Commented Feb 10, 2013 at 13:11

4 Answers 4

var counts = {};
yourstring.split('').map(function(ch) {
  counts[ch] = (counts[ch] || 0) + 1;
});

Or be hip and use map/reduce:

var counts = yourstring.split('').reduce(function(dst, c) {
  dst[c] = (dst[c] || 0) + 1;
  return dst;
}, {});

this code should work:

var str = "Hello World";
var arr = str.split('');
var occ = {};
for(var i=0,c=arr.length;i<c;i++){
    if(occ[arr[i]]) occ[arr[i]]++;
    else occ[arr[i]] = 1;
}
for(var i in occ){
    alert('count of '+i+' -> '+occ[i]); 
}

var splitWord = "Hello World".split('');
var letters = {};
for(var i in splitWord)
{
    var letter = splitWord[i];
    if(letter == ' ') continue;
    if(typeof letters[letter] == 'undefined')
    {
        letters[letter] = 0;
    }
    letters[letter]++;
}
console.dir(letters);

Below is my solution with the old and simple for loop. This approach answers the question in the simplest possible way for beginners. This code will convert all the letters in the input to lower case and count their occurrence. In this solution, we also count the special characters and spaces as valid characters.

  function countChar(str) {
            var count = {};
            for (let i = 0; i < str.length; i++) {
                var ch = str[i].toLowerCase();
                if (count[ch] > 0) {
                    count[ch]++;
                } else {
                    count[ch] = 1;
                }
            }
            return count;
        }

The count object denotes the characters in the input.