Unique letters in a string using reduce

unique-letters-in-a-string.js

function getLetterCount(arr){
    return arr.reduce(function(prev,next){
        prev[next] = (prev[next] + 1) || 1;
        console.log(prev[next]);
        return prev;
    },{});
}

var str = "dfdddf";

console.log(getLetterCount(str.split('')));