Why “this” inside of a function's returning object window

Question

there is two type of scope in javascript named function scope global scope

now i am executing this code

function abc()
{
alert(this)         


        

Answer 1

this, inside any function, will be the object on which the function is invoked. In your case, you are not invoking it on any object. So, by default this refer to global object, in your browser, it is the window object.

But in strict mode, if you invoke it like this, this will be undefined.

"use strict";
function abc() {
    console.log(this);    // undefined
}
abc();

Or

function abc() {
    "use strict";
    console.log(this);   // undefined
}
abc();