This article does two things that are very dangerous, and never mentions the reasons why they're dangerous.
* Messing with Function's prototype is very strongly frowned upon. It's tantamount to setting global variables. At the very least, give that definition an if (!Function.new) guard to prevent redefining another implementation that another script (or the browser!) has already given.
* Adding methods in the constructor is awful even if you're not using inheritance, because it burns memory like crazy. If you define sayHi on Person.prototype, then every Person gets a reference to the same sayHi method. If you define this.sayHi in the constructor, then each Person you create gets its own copy of the function, making every Person heavier in memory. Not a big deal for a simple console.log, but if you have more complicated objects with a few dozen methods that you're using a bunch of you can really make things chug.
* Messing with Function's prototype is very strongly frowned upon. It's tantamount to setting global variables. At the very least, give that definition an if (!Function.new) guard to prevent redefining another implementation that another script (or the browser!) has already given.
* Adding methods in the constructor is awful even if you're not using inheritance, because it burns memory like crazy. If you define sayHi on Person.prototype, then every Person gets a reference to the same sayHi method. If you define this.sayHi in the constructor, then each Person you create gets its own copy of the function, making every Person heavier in memory. Not a big deal for a simple console.log, but if you have more complicated objects with a few dozen methods that you're using a bunch of you can really make things chug.