JavaScript DYI map, filter, reduce

index.js

const arr = [1, 2, 3, 4, 1, 2, 3]; 

const originalMap = arr.map(i => i + 1);

const myMap = (arr, cb) => {
  let temp = []; 
  
  for(let i = 0; i < arr.length; i++) {
      temp.push(cb(arr[i]));
  }
  
  return temp;
}

const myMapTest = myMap(arr, (i => i + 1));

const originalFilter = arr.filter(i => i === 1);

const myFilter = (arr, cb) => {
  let temp = [];

  for(let i = 0; i < arr.length; i++) {
      if (cb(arr[i])) temp.push(arr[i]);
  } 
  
  return temp;
}

const myFiltertest = myFilter(arr, (i => i === 1));

const originalReduce = arr.reduce((a, b) => a + b); 

const myReduce = (arr, cb, init = arr[0]) => {
  let temp = init; 
  
  for(let i = 0; i < arr.length; i++) {
    temp = cb(temp, arr[i]);
  }

  return temp;
}

console.log(myReduce(arr, (a, b) => a * b))