Functional Programming - Implement map on a Prototype

JavaScript
1

Tell us what’s happening:
Describe your issue in detail here.
Could someone please explain why the callback function has 3 parameters (this[I], I, this) initially my code just had 1 parameter for the callback function (this[I]) but I don’t understand why (I, this) are also parameters and what they do
Your code so far

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;
};

Your browser information:

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.5 Safari/605.1.15

Challenge: Functional Programming - Implement map on a Prototype

Link to the challenge:

3

If you still have questions, about this.

Allow me to answer.

[1, 1, 2, 5, 2].myMap((element, index, array) => array[index + 1] || array[0])

The callback function has three parameters when it is being called.

this refers to the object the function was called on. i is the index of the the new array. The first parameter is the element. Then it’s an index. Then the new array.

4

This topic was automatically closed 182 days after the last reply. New replies are no longer allowed.