Polyfill of Array's map, filter and reduce methods

arrays-polyfill.js

// reduce
Object.defineProperty(Array.prototype, 'myReduce', {
  value: function(fn, initial) {
    let values = this;

    values.forEach((item, idx) => {
        initial = fn(initial, item, idx)
    })

    return initial;
  }
})

// map
Object.defineProperty(Array.prototype, 'myMap', {
  value: function(fn) {
    let storage = [];
  
    for (let i = 0; i < this.length; i++) {
      storage.push(fn(this[i], i));
    }
  
    return storage;
  }
})

// filter
Object.defineProperty(Array.prototype, 'myFilter', {
  value: function(fn) {
    let storage = [];
  
    for (let i = 0; i < this.length; i++) {
      if (fn(this[i], i)) {
          storage.push(this[i]);
      }
    }
  
    return storage;
  }
})

This snippet is created for creaking interviews but in reality, using this is polyfill is very risky so please don't use on production.