Factory & Constructor Functions

function Car(make) {
  this.make = make;
}

const car = Car('Toyota');
console.log(car?.make);
console.log(window.make);

undefined, undefined
Toyota, undefined
undefined, Toyota
Since Car is called without the 'new' keyword, 'this' inside the function refers to the global object (window in browsers). Therefore, car will be undefined (as no return value is specified), and make becomes a property of the global object. This is a common pitfall when forgetting to use 'new' with constructor functions. Using 'new' would create a new object and bind 'this' to it instead.
Toyota, Toyota