Own version of map, reduce and filter (ES6)

mapReduceFilter.js

// map
const map = (arr, func) => {
  
  const outputArr = [];
  
  for (let i = 0; i<arr.length; i++ ){
    outputArr.push(func(arr[i]));
  }
  return outputArr;
}

const multiply2 = num => num*2;
const multiply3 = num => num*3;
const square = num => num*num;

const answer1 = map([1,2,3],multiply2);
const answer2 = map([1,2,3],multiply3);
const answer3 = map([1,2,3],square);



console.log(answer1,answer2, answer3);

// reduce function
const reducer = (arr, callB, initial) => {
  
  for (let i = 0; i<arr.length; i++ ){
    initial = callB(arr[i], initial);
  }
  return initial;
}

const add = (val,val2) => val+val2;

const answer = reducer([2,3,4], add,0);

console.log(answer);

// filter 
const filter = (arr , condition) => {
  
  const newArr = [];
  
  for(let i = 0; i < arr.length; i ++){
    
    if(condition(arr[i])) newArr.push(arr[i]);
  }
  
  return newArr;
  
}

const isEven = num => (num%2 === 0) ? true : false;

const isOdd = num => (isEven(num)) ? false : true;


console.log(filter([0,2,4,6,8,9],isEven));
console.log(filter([0,2,4,6,8,9],isOdd));