Prototype / Polyfill function for JavaScript Array map
The `map()` function is a built-in method in JavaScript that is used to create a new array by performing a given operation on each element of the original array. The prototype function for `map()` can be written as follows:
Array.prototype.myMap = function(callback) {
let result = [];
for(let i=0; i<this.length; i++) {
result.push(callback(this[i], i, this));
}
return result;
}
In this function, we have created a new prototype method called `myMap()` for the `Array` object, which takes a callback function as an argument. The callback function is the operation that will be performed on each element of the original array.
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Inside the function, we initialize an empty array called `result` that will hold the mapped values. We then loop through each element of the original array using a `for` loop. For each element, we call the `callback` function with three arguments: the current element, its index, and the original array. The `callback` function returns the mapped value, which we push to the `result` array.
Finally, we return the `result` array, which contains all the mapped values.
This prototype function can be used like the built-in `map()` method, as shown below:
const numbers = [1, 2, 3, 4, 5];
const doubled = numbers.myMap(num => num * 2);
console.log(doubled); // Output: [2, 4, 6, 8, 10]In this example, we use `myMap()` to double each element of the `numbers` array and store the results in a new array called `doubled`. The output is then printed to the console.
