I recently heard about higher-order functions and I’m curious about how they work internally.

For example, consider this code:

```
var numbers = [16, 25, 36];
var results = numbers.map(Math.sqrt);
console.log(results); // [4, 5, 6]
```

What is the mechanism that allows each element of the `numbers`

array to be iterated through one by one?

I have done some research, but I have yet to find a satisfactory answer.

The `map`

function in JavaScript is a higher-order function that takes a callback function as an argument.

When you use `numbers.map(Math.sqrt)`

, it internally iterates over each element in the `numbers`

array and applies the `Math.sqrt`

function to each element. The `Math.sqrt`

function calculates the square root of a number.

The `map`

function takes care of iterating over each element in the array and applies the callback function to each element. It then collects the results of each function call and returns a new array containing the results.

In your example, `numbers.map(Math.sqrt)`

applies the `Math.sqrt`

function to each element in the `numbers`

array, resulting in a new array `[4, 5, 6]`

, which is then assigned to the `results`

variable.

So, the mechanism that allows each element of the `numbers`

array to be iterated through one by one is the higher-order function `map`

.