Clarifying this in javascript example 1

gistfile1.txt

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 is the direct-parent foo object context
  },
};

foo.getBar()                // logs 'baz'

const qux = foo.getBar;     // assigning the function stored as the method getBar to the variable qux in the global scope

qux()                       // logs undefined, then returns undefined  =>  why?