JS this dynamic scoping [duplicate]

When trying to execute the following snippet, I expected the doFoo.call(obj, obj.foo) call to return "inside obj" as the dynamic scope of the previous element in the call stack has a reference to a but the call has the global context instead. What am I missing here?

function foo() {
  // debugger
  console.log(this, this.a);
}

function doFoo(fn) {
  // `fn` is just another reference to `foo`
  // debugger 
  fn()
  // <-- call-site!
}

var obj = {
  a: 'inside obj',
  foo: foo
};

var a = "oops, global"; // `a` also property on global object

doFoo(obj.foo); // "oops, global"
doFoo.call(obj, obj.foo) // "oops, global"```

Via Active questions tagged javascript - Stack Overflow https://ift.tt/BpEImlW