Question

In JavaScript

What is the result? Make sure you can explain why. let arr = ["a", "b"]; arr.push(function() { alert( this ); }) arr[2](); // ?

Answer 1

the output is shown in the image above. the thing we are doing here, is known as Closure, a very prominent feature of javascript.

We first created an array of 2 elements. Then we appended a function on the 3rd position of the array and then when we say arr[2](), then we are basically calling this function.

Inside the function body, we use alert(this); this always refers to the object in enclosing scope, which in this case is the array arr, because it keeps the function inside it.. Hence when we say alert(this), the entire content of array are string represented on the alert popup that you see above.

hope it clarifies.