I don't understand how a prototype function (1) returns a array and then that array is iterated to the argument of the function (1)?

JavaScript
1

Tell us what’s happening:
Describe your issue in detail here.
The ’ Mymap ’ function takes a function as argument. Then it returns a array.
The part I don’t understand is How the array returned by Mymap function is iterated into the function that was the argument of the Mymap function ???

  **Your code so far**


// 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;
});

  **Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.71 Safari/537.36

Challenge: Implement map on a Prototype

Link to the challenge:

2

Look at what the myMap function is doing in the for loop:

newArray.push(callback(this[i]));

It is calling the callback function for each element in the array. So the function you passed into myMap is being applied to every element in the array.

3

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