context.html

<!DOCTYPE html>
<html>
<body>

<h2>Context</h2>
<p>Open console to check</p>
<script>
console.log(this); // print window object

var a = 1;
console.log(this.a); // print value 1
console.log(a); // print value 1

function foo() {
    console.log(this);
}
foo(); // print window object becuase by deault it will take window.foo()

var obj = {
    foo: function(){
        console.log(this); // print object foo: ƒ ()
    }
}
obj.foo();
obj.foo.apply();
obj.foo.call();
var mybound = obj.foo.bind(window);
mybound();

</script>
</body>
</html> 