public/subjects/animals

Animals

Instructions

Modern JavaScript implements high level tools for creating and managing classes, nevertheless most of those tools rely on low level functions still present and in use in many libraries and legacy code.

In order to understand how prototypal inheritance works you will have to recreate a similar behavior by using only the low level functions provided by the language.

You will have Animal which will an object and will have the following properties:

• canEat, canBreath, isAlive: All booleans, set to true.
• name: set to "Anonymous".
• WhoAmI: Function that returns a string, here it will be "I'm an animal".
• NameToUppercase: Function that returns name to uppercase.

The following objects will inherit from Animal and add/override fields as follow:

• Dog: adds property canRun set to true.

• Bird: adds properties canFly and makesEggs set to true.

• Dodo: inherits from Bird and overrides canFly and isAlive to false.

• All of them will override WhoAmI, returning "I'm a [animal name]".

• All can accept a specific name as argument when created or use the default in Animal if no argument is provided.

There are many different ways to work on prototypes, we suggest to use Object.assign and similar functions, but feel free to experiment other ways to understand the differences.

Usage

Here is a possible program to test your function:

// Your implementation of Animal, Dog, Bird and Dodo ...

const myDog = new Dog()
const myBird = new Bird("Trill")
const myDodo = new Dodo("Mallone")
console.log("canEat: " + myDog.canEat + " | hasOwn: " + Object.hasOwn(myDog, "canEat"))
console.log("canEat: " + myBird.canEat + " | hasOwn: " + Object.hasOwn(myBird, "canEat"))
console.log("canEat: " + myDodo.canEat + " | hasOwn: " + Object.hasOwn(myDodo, "canEat"))
console.log("canRun: " + myDog.canRun + " | hasOwn: " + Object.hasOwn(myDog, "canRun"))
console.log("canFly: " + myBird.canFly + " | hasOwn: " + Object.hasOwn(myBird, "canFly"))
console.log("canFly: " + myDodo.canFly + " | hasOwn: " + Object.hasOwn(myDodo, "canFly"))
console.log("makesEggs: " + myDodo.makesEggs + " | hasOwn: " + Object.hasOwn(myDodo, "makesEggs"))
console.log("WhoAmI: " + myDog.WhoAmI() + " | hasOwn: " + Object.hasOwn(myDog, "WhoAmI"))
console.log("WhoAmI: " + myBird.WhoAmI() + " | hasOwn: " + Object.hasOwn(myBird, "WhoAmI"))
console.log("WhoAmI: " + myDodo.WhoAmI() + " | hasOwn: " + Object.hasOwn(myDodo, "WhoAmI"))
console.log("name: " + myDog.name + " | hasOwn: " + Object.hasOwn(myDog, "name"))
console.log("name: " + myBird.name + " | hasOwn: " + Object.hasOwn(myBird, "name"))
console.log("name: " + myDodo.name + " | hasOwn: " + Object.hasOwn(myDodo, "name"))
console.log("NameToUppercase: " + myDog.NameToUppercase() + " | hasOwn: " + Object.hasOwn(myDog, "NameToUppercase"))
console.log("NameToUppercase: " + myBird.NameToUppercase() + " | hasOwn: " + Object.hasOwn(myBird, "NameToUppercase"))
console.log("NameToUppercase: " + myDodo.NameToUppercase() + " | hasOwn: " + Object.hasOwn(myDodo, "NameToUppercase"))

And its output :

$ node animals.js
canEat: true | hasOwn: false
canEat: true | hasOwn: false
canEat: true | hasOwn: false
canRun: true | hasOwn: true
canFly: true | hasOwn: true
canFly: false | hasOwn: true
makesEggs: true | hasOwn: true
WhoAmI: I'm a dog | hasOwn: true
WhoAmI: I'm a bird | hasOwn: true
WhoAmI: I'm a dodo | hasOwn: true
name: Anonymous | hasOwn: false
name: Trill | hasOwn: true
name: Mallone | hasOwn: true
NameToUppercase: ANONYMOUS | hasOwn: false
NameToUppercase: TRILL | hasOwn: false
NameToUppercase: MALLONE | hasOwn: false
$

Notions

• Object prototypes

• Object.assign()