Functional Programming: Implement map on a Prototype

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Functional Programming: Implement map on a Prototype

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Functional Programming: Implement map on a Prototype

As you have seen from applying Array.prototype.map(), or simply map() earlier, the map method returns an array of the same length as the one it was called on. It also doesn't alter the original array, as long as its callback function doesn't.

In other words, map is a pure function, and its output depends solely on its inputs. Plus, it takes another function as its argument.

It would teach us a lot about map to try to implement a version of it that behaves exactly like the Array.prototype.map() with a for loop or Array.prototype.forEach().

Note: A pure function is allowed to alter local variables defined within its scope, although, it's preferable to avoid that as well.

Write your own Array.prototype.myMap(), which should behave exactly like Array.prototype.map(). You may use a for loop or the forEach method.

script.js

// the global Array
var s = [23, 65, 98, 5];

Array.prototype.myMap = function(callback){
  var newArray = [];
  // Add your code below this line
  for(let i = 0; i < this.length ; i++ ){
  newArray.push(callback(this[i]));}
  // Add your code above this line
  return newArray;

};

var new_s = s.myMap(function(item){
  return item * 2;
});

If arr have more object, How will you handle it???

Much better answer than above solution to the problem - [ Functional Programming: Implement map on a Prototype ]

// The global variable
const s = [23, 65, 98, 5];

Array.prototype.myMap = function(callback) {
  const newArray = [];
  // Only change code below this line
  s.forEach((callback)=>(newArray.push(callback * 2)));
  // Only change code above this line
  return newArray;
};

const new_s = s.myMap(function(item) {
  return item * 2;
});
console.log(new_s);

@Rupesh-Darimisetti yours is incorrect. you're doing the function in the map method itself. the value of new_s should affect the callback, not the other way round. thus, the solution above yours is still the answer.

var array1 = [23, 65, 98, 5, 13]
var array2 = ["naomi", "quincy", "camperbot"]
var array3 = [1, 1, 2, 5, 2]

Array.prototype.myMap = function(callback){
var newArray = [];
// Add your code below this line
for(let i = 0; i < this.length ; i++ ){
// callback(this[i], i)
newArray.push(callback(this[i], i, this));
}
// Add your code above this line
return newArray;
};

var new_s = array1.myMap(function(item){
return item * 2;
});

var new_s2 = array2.myMap(function(item){
return item.toUpperCase();
});
var new_s3 = array3.myMap(function(itens, index, array){
return array[index + 1] || array[0];
});

I would like to know if this line of reasoning would be correct for solving the exercise

Yeah @gabrielmanoel-hub , among all the provided solution, your solution would definetely work for all the test cases.

Array.prototype.myMap = function(callback) {
const newArray = [];
// Only change code below this line
for(let i = 0; i < this.length; i++){
newArray.push(callback(this[i], i , this))}

// Only change code above this line
return newArray;

};

Thanks