what is this in javascript

                                    var wF = {
    w : 560,
    h : function() { return (312 - 42) / (560 / this.w) + 42; }
};

alert(wF.h())

                                    
"use strict";
function myFunction() {

    return this;

}
 

                                    // Im Webbrowser ist das window Objekt das globale Objekt:
console.log(this === window); // true

a = 37;
console.log(window.a); // 37

this.b = "MDN";
console.log(window.b);  // "MDN"
console.log(b);         // "MDN"

                                    The JavaScript this keyword refers to the object it belongs to. 
It has different values depending on where it is used: In a method, 
this refers to the owner object. Alone, this refers to the global 
object.

                                    // In web browsers, the window object is also the global object:
console.log(this === window); // true

a = 37;
console.log(window.a); // 37

this.b = "MDN";
console.log(window.b)  // "MDN"
console.log(b)         // "MDN"