DEV-4017-prototypes-exercise-1-animals

js/tests/animals_test.js

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+export const tests = []
+const t = f => tests.push(f)
+
+// Test Dog
+t(({ eq }) => {
+  const Animal = {
+    canEat: false,
+  }
+  Object.assign(Dog.prototype, Animal)
+
+
+  let myDog = new Dog()
+  return eq(
+    { 
+      redefinedCanEat: myDog.canEat,
+      hasOwn: Object.hasOwn(myDog, 'canEat'),
+      canBreath: myDog.canBreath,
+      hasOwn: Object.hasOwn(myDog, 'canBreath'),
+      isAlive: myDog.isAlive,
+      hasOwn: Object.hasOwn(myDog, 'isAlive'),
+      canRun: myDog.canRun,
+      hasOwn: Object.hasOwn(myDog, 'canRun'),
+      WhoAmI: myDog.WhoAmI(),
+      hasOwn: Object.hasOwn(myDog, 'WhoAmI'),
+    },
+    { 
+      redefinedCanEat: false,
+      hasOwn: false,
+
+      canBreath: true,
+      hasOwn: false,
+      isAlive: true,
+      hasOwn: false,
+      canRun: true,
+      hasOwn: true,
+      WhoAmI: "I'm a dog",
+      hasOwn: true,
+    })
+})
+
+// Test Bird
+t(({ eq }) => {
+  let myBird = new Bird()
+  return eq(
+    { 
+      canEat: myBird.canEat,
+      hasOwn: Object.hasOwn(myBird, 'canEat'),
+      canBreath: myBird.canBreath,
+      hasOwn: Object.hasOwn(myBird, 'canBreath'),
+      isAlive: myBird.isAlive,
+      hasOwn: Object.hasOwn(myBird, 'isAlive'),
+      makesEggs: myBird.makesEggs,
+      hasOwn: Object.hasOwn(myBird, 'makesEggs'),
+      canFly: myBird.canFly,
+      hasOwn: Object.hasOwn(myBird, 'canFly'),
+      WhoAmI: myBird.WhoAmI(),
+      hasOwn: Object.hasOwn(myBird, 'WhoAmI'),
+    },
+    { 
+      canEat: true,
+      hasOwn: false,
+      canBreath: true,
+      hasOwn: false,
+      isAlive: true,
+      hasOwn: false,
+      makesEggs: true,
+      hasOwn: true,
+      canFly: true,
+      hasOwn: true,
+      WhoAmI: "I'm a bird",
+      hasOwn: true,
+    })
+})
+
+// Test Dodo
+t(({ eq }) => {
+  let myDodo = new Dodo()
+  return eq(
+    { 
+      canEat: myDodo.canEat,
+      hasOwn: Object.hasOwn(myDodo, 'canEat'),
+      canBreath: myDodo.canBreath,
+      hasOwn: Object.hasOwn(myDodo, 'canBreath'),
+      isAlive: myDodo.isAlive,
+      hasOwn: Object.hasOwn(myDodo, 'isAlive'),
+      makesEggs: myDodo.makesEggs,
+      hasOwn: Object.hasOwn(myDodo, 'makesEggs'),
+      canFly: myDodo.canFly,
+      hasOwn: Object.hasOwn(myDodo, 'canFly'),
+      WhoAmI: myDodo.WhoAmI(),
+      hasOwn: Object.hasOwn(myDodo, 'WhoAmI'),
+    },
+    { 
+      canEat: true,
+      hasOwn: true,
+      canBreath: true,
+      hasOwn: true,
+      isAlive: false,
+      hasOwn: true,
+      makesEggs: true,
+      hasOwn: true,
+      canFly: false,
+      hasOwn: true,
+      WhoAmI: "I'm a dodo",
+      hasOwn: true,
+    })
+})
+
+// Test Dodo
+t(({ eq }) => {
+  let myDog = new Dog("Rex")
+  let myBird = new Bird()
+  let myDodo = new Dodo("Dill")
+  return eq(
+    { 
+      name: myDog.name,
+      hasOwn: Object.hasOwn(myDog, 'name'),
+      name: myBird.name,
+      hasOwn: Object.hasOwn(myBird, 'name'),
+      name: myDodo.name,
+      hasOwn: Object.hasOwn(myDodo, 'name'),
+    },
+    { 
+      name: "Rex",
+      hasOwn: true,
+      name: "Anonymous",
+      hasOwn: false,
+      name: "Dill",
+      hasOwn: true,
+    })
+})
+
+export const setup = () => {
+}
+
+Object.freeze(tests)

subjects/animals/README.md

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+## 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:
+
+```javascript
+// 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 :
+
+```console
+$ 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](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/Object_prototypes)
+
+- [Object.assign()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign?retiredLocale=it)