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

Your function is under global(window) object. I mean,

function abc()
{
    alert(this);
}
abc(); 
// or You can either call by
window.abc()

You can write your function under custom object

// Function under custom object
var customObj = {
    abc : function () {
        alert(this);
    }
};
customObj.abc()