for-loop.js

let string = "aabbbcbck"
let strArr = string.split("") // [ 'a', 'a', 'b', 'b', 'b', 'c', 'b', 'c', 'k' ]

// Array to object using For-Loop - counting each letter occurances
let usingForLoop = (arr)=>{
  let newObj={};
  for(let i=0; i<arr.length; ++i){
      newObj[arr[i]] = newObj[arr[i]]+1 || 1;
    }
  return newObj;
}
console.log("using For Loop: ", usingForLoop(strArr)) //{ a: 2, b: 4, c: 2, k: 1 }