Question

This question is from ECMA-262 quiz

var x = 100;
var foo = {
  x: 50,
  bar: function(){
    return this.x;
  }
}
console.log(foo.bar()); //returns 50
console.log((foo.bar = foo.bar)()); //returns 100

How does the this context changes in the second console statement ? or in general what object does equals to(assigning) operation returns the global object ?

Answer 1

foo.bar (a member operator) evaluates to a Reference “the property “bar” on an object“, and this will be treated special when calling it.

(foo.bar = foo.bar) (an assignment) just yields the assigned value, and calling it will result in the global object being used as this.