Implementation of Map, Filter, and Reduce on an Object to iterate through its keys

mapFilterReduceOnObject.js

let map = (f, o) => {
  //o must be an object
  let keys = Object.keys(o);
  let ret = {};
  for (let i = 0; i <= keys.length - 1; i++) {
   let key = keys[i];
   let val = o[key];
   ret[key] = f(val, key);
  }
  return ret;
}

let filter = (f, o) => {
  //o must be an object
  let keys = Object.keys(o);
  let ret = {};
  for (let i = 0; i <= keys.length - 1; i++) {
   let key = keys[i];
   let val = o[key];
   if (f(val, key)) {
     ret[key] = val;
   }
  }
  return ret;
}

let reduce = (f, a, o) => {
  let keys = Object.keys(o);
  let acc = a;
  for (let i = 0; i <= keys.length - 1; i++) {
   let key = keys[i];
   let val = o[key];
   acc = f(acc, val, key);
  }
  return acc;
}

let o = {
  a: "hello",
  b: "world",
  c: "!"
}

let p = map((v, k) => `${v}!(${k})`, o)

console.log(p)

let q = filter((v, k) => (v === 'hello' || k === 'b'), o)

console.log(q)

let r = reduce((acc, v, k) => `${acc} ${v}`, "", o)

console.log(r)