Code from an interview question about 'this'

this.js

var foo = {
  a: function () {
    console.log(this);
  }
};

foo.a();
// => foo

foo['a']();
// => foo

var someAsync = function (cb) {
  cb();
};

someAsync(foo.a);
// => Window

setTimeout(foo.a, 0)
// => Window

someAsync(foo.a.bind(foo));
// => foo

setTimeout(foo.a.bind(foo), 0);
// => foo