Clairifying this in Javascript example 4

this_js_ex4.js

const foo = {
  bar: 10,
  multiplyByBar: function(...args) {
    args.forEach(function(arg) {
      console.log(arg * this.bar);
    }, this);
  }
};

const qux = foo.multiplyByBar.bind(foo);
foo.bar = 100;

qux(5);           // logs 500
qux(5, 10, 15);   // logs 500, then 1000, then 1500