Clarifying This in JavaScript example 1

this_js_ex1.js

const foo = {
  bar: 'baz',
  getBar: function() {     // assigned as a property on an object, getBar is a method
    console.log(this.bar); // the value of this here: foo
  },
};

foo.getBar()               // logs 'baz'

let qux = foo.getBar;      // assigning the function getBar to the variable qux
qux()                      // logs undefined, then returns undefined  =>  why?