Long Practice: Context

In this practice, you will practice debugging more context problems.

Set up

Clone the starter from the Download link at the bottom of this page.

Run npm install to install any dependencies.

Phase 1: Car

Implement the following in the problems/01-car-drive.js file.

1. Create a Car class.
2. A newly instantiated instance should have its speed property initialized to 0.
3. Add an instance method called drive(newSpeed) that takes in a newSpeed and sets it to the instance's speed property. It should also return the present speed of the instance.

Test your implementation by running the test specs in the test/01-car-drive-spec.js file. Run the specs with the following command:

npm test test/01-car-drive-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Examples:

let car = new Car();
car.drive(0);     // => returns 0
console.log(car); // => { speed: 0 }

car.drive(10);    // => returns 10
console.log(car); // => { speed: 10 }

car.drive(50);    // => returns 50
console.log(car); // -> { speed: 50 }

car.drive(100);   // => returns 100
console.log(car); // -> { speed: 100 }

Phase 2: Calculator

Implement the following in the problems/02-calculator.js file.

1. Create a Calculator class.
2. A newly instantiated instance should have its total property initialized to 0.
3. Add the following instance methods which should all return the reassigned total property of the instance: a. add(num) - add the num arg to the total b. subtract(num) - subtract the num arg from the total c. divide(num) - divide the total by the num arg d. multiply(num) - multiply the total by the num arg

Test your implementation by running the test specs in the test/02-calculator-spec.js file. Run the specs with the following command:

npm test test/02-calculator-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Examples:

let calculator = new Calculator();
console.log(calculator.add(50));      // => 50
console.log(calculator.subtract(35)); // => 15
console.log(calculator.multiply(10)); // => 150
console.log(calculator.divide(5));    // => 30
console.log(calculator.total)         // => 30

Phase 3: Dog

Implement the following in the problems/03-make-dog.js file.

1. Create a Dog class.
2. The constructor function should take in a name argument and set the name property of a newly instantiated instance to the name argument.
3. Add a static method called makeJet() that will return a new instance of the Dog class with a name property of "Jet".
4. Add two instance methods: a. changeName(newName) - set the name to the newName b. speak(word) - returns ${name} says ${word}

Test your implementation by running the test specs in the test/03-make-dog-spec.js file. Run the specs with the following command:

npm test test/03-make-dog-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Examples:

let dog1 = Dog.makeJet(); // returns an object

console.log(dog1.name);                 // Jet
console.log(dog1.speak("hello"));       // Jet says hello
console.log(dog1.changeName("Freyja")); // Freyja
console.log(dog1.name);                 // Freyja
console.log(dog1.speak("hello"));       // Freyja says hello

let dog2 = Dog.makeJet();
console.log(dog2.name);                 // Jet

Phase 4: changeContext(func, obj)

Implement the following in the problems/04-change-context.js file.

Write a function named changeContext(func, obj) that will accept a function func and an object obj. The changeContext function should return the result of the function func invoked with the object obj as its context.

Test your implementation by running the test specs in the test/04-change-context-spec.js file. Run the specs with the following command:

npm test test/04-change-context-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Example:

class Person {
  constructor(name) {
    this.name = name;
  }
}

function extractName() {
  return this.name;
}

const kristen = new Person('Kristen');
console.log(changeContext(extractName, kristen)); // => Kristen

Phase 5: bindToAnArg(func, arg)

Implement the following in the problems/05-bind-to-an-arg.js file.

Write a function named bindToAnArg(func, arg) that will accept a function func and any argument arg. The bindToAnArg function should return the passed-in function func modified to always be invoked with the passed-in argument arg.

Test your implementation by running the test specs in the test/05-bind-to-an-arg-spec.js file. Run the specs with the following command:

npm test test/05-bind-to-an-arg-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Examples:

function add(num1, num2) {
  return num1 + num2;
}

const addTwo = bindToAnArg(add, 2);
const addThree = bindToAnArg(add, 3);

const twoPlusSix = addTwo(6);
const twoPlusSeven = addTwo(7);
const threePlusSeven = addThree(7);
const threePlusEight = addThree(8);
console.log({
  twoPlusSix,     // => 8
  twoPlusSeven,   // => 9
  threePlusSeven, // => 10
  threePlusEight  // => 11
});

function iSpy(thing) {
  return "I spy a " + thing;
}

let spyTree = bindToAnArg(iSpy, "tree");
console.log(spyTree());        // => I spy a tree
console.log(spyTree("car"));   // => I spy a tree

let spyCar = bindToAnArg(iSpy, "car");
console.log(spyCar());         // => I spy a car
console.log(spyCar("potato")); // => I spy a car

Phase 6: FancyCalculator

Implement the following in the problems/06-fancy-calculator.js file.

1. Import the Calculator class.
2. Create a FancyCalculator class with the Calculator class as its parent class.
3. Add the following instance methods which should all return the reassigned total property of the instance: a. setTotal(newTotal) - sets the total to the newTotal b. modulo(num) - sets the total to the remainder of dividing by num c. squared() - multiplies the total by the total

Test your implementation by running the test specs in the test/06-fancy-calculator-spec.js file. Run the specs with the following command:

npm test test/06-fancy-calculator-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Examples:

let fancyCalculator = new FancyCalculator();
console.log(fancyCalculator.setTotal(5)); // => 5
console.log(fancyCalculator.squared());   // => 25
console.log(fancyCalculator.modulo(4));   // => 1
console.log(fancyCalculator.total)        // => 1

// can use instance methods on the Calculator class
console.log(fancyCalculator.add(9))       // => 10

Phase 7: allTheArgs(func, ...args)

Implement the following in the problems/07-all-the-args.js file.

Write a function named allTheArgs(func, ...args) that will accept a function func and any number of arguments. Then return the string "You bowed to" concatenated to the array of args. The allTheArgs function should return the passed-in function func modified to always be invoked with the passed-in arguments args. See code block below for further details.

Test your implementation by running the test specs in the test/07-all-the-args-spec.js file. Run the specs with the following command:

npm test test/07-all-the-args-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

function sum(...nums) {
  return nums.reduce((acc, num) => acc + num);
}

const onePlusTwo = allTheArgs(sum, 1, 2);

const onePlusTwoPlusThree = onePlusTwo(3);
const onePlusTwoPlusFour = onePlusTwo(4);

console.log(onePlusTwoPlusThree); // => 6
console.log(onePlusTwoPlusFour);  // => 7

const bow = (...names) => {
  return "You bowed to " + names.join(" and ");
};

console.log(bow("Sandy")) // prints "You bowed to Sandy"

let bowSandy = allTheArgs(bow, "Sandy");
console.log(bowSandy()); // prints "You bowed to Sandy"
console.log(bowSandy("Joe", "Nico")); // prints "You bowed to Sandy and Joe and Nico"

Phase 8: CallCenter

Implement the following in the problems/08-call-me-later.js file.

1. Create a CallCenter class.
2. The constructor function should take in a name argument and set the name property of a newly instantiated instance to the name argument.
3. Add two instance methods: a. sayHello() - prints Hello this is ${name} b. callMeLater(delay) - takes in a delay in milliseconds that will call the sayHello() method on the instance after the delay. The context of the sayHello() method when invoked needs to be the CallCenter instance that the method was called on.

You CANNOT use bind, call, or apply for this phase!

Test your implementation by running the test specs in the test/08-call-me-later-spec.js file. Run the specs with the following command:

npm test test/08-call-me-later-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Example 1:

let judy = new CallCenter("Judy");
judy.sayHello();         // prints "Hello this is Judy"
judy.callMeLater(1000);  // waits one second then prints "Hello this is Judy"

Example 2:

let melan = new CallCenter("Melan");
melan.sayHello();        // prints "Hello this is Melan"
melan.callMeLater(1000); // waits one second then prints "Hello this is Melan"

Phase 9: callOnTarget(func, obj1, obj2)

Implement the following in the problems/09-call-on-target.js file.

Write a function named callOnTarget(func, obj1, obj2) that will accept a function func and two objects, obj1 and obj2. callOnTarget should return the result of the function func invoked with obj1 as its context and obj2 as the first argument.

Test your implementation by running the test specs in the test/09-call-on-target-spec.js file. Run the specs with the following command:

npm test test/09-call-on-target-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Examples:

const cat = {
  name: "Breakfast"
};

const mouse = {
  name: "Jerry"
};

function greet(other) {
  return "I'm " + this.name + ". Nice to meet you, " + other.name;
}

console.log(callOnTarget(greet, cat, mouse));
// "I'm Breakfast. Nice to meet you, Jerry"

console.log(callOnTarget(greet, mouse, cat));
// "I'm Jerry. Nice to meet you, Breakfast"

const dog = {
  name: "Noodles",
  chase: function(animal) {
    return "Woof, my name is " + this.name + " and I'm chasing " + animal.name;
  }
};

console.log(callOnTarget(dog.chase, cat, dog));
// "Woof, my name is Breakfast and I'm chasing Noodles"

Phase 10: PartyPlanner

Implement the following in the problems/10-party-planner.js file.

1. Create a PartyPlanner class.
2. A newly instantiated instance should have its guestList property initialized to an empty array.
3. Add two instance methods: a. addToGuestList(name) - add the name to the guestList b. throwParty() - return a different string depending on the length of the guestList:
   • If there are no guests, return "Gotta add people to the guest list"
   • If there are guests in the guestList, return the guests' names. For example, if there are two guests, return "Welcome to the party ${name1} and ${name2}".

Test your implementation by running the test specs in the test/10-party-planner-spec.js file. Run the specs with the following command:

npm test test/10-party-planner-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Example 1:

const party = new PartyPlanner();

console.log(party.throwParty()); // prints "Gotta add people to the guest list"

party.addToGuestList("James");
console.log(party.throwParty()); // prints "Welcome to the party James"

party.addToGuestList("Alvin");
console.log(party.throwParty()); // prints "Welcome to the party James and Alvin"

Example 2:

const party2 = new PartyPlanner();
console.log(party2.throwParty()); // prints "Gotta add people to the guest list"

party2.addToGuestList("Lucy");
console.log(party2.throwParty()); // prints "Welcome to the party Lucy"

Phase 11: boundFuncTimer(obj, func, delay)

Implement the following in the problems/11-bind-set-timeout.js file.

Write a function named boundFuncTimer(obj, func, delay) that will accept am object obj, a function func, and delay which is a number representing milliseconds. The boundFuncTimer should invoke the function func with obj as its context after a delay.

Test your implementation by running the test specs in the test/11-bind-set-timeout-spec.js file. Run the specs with the following command:

npm test test/11-bind-set-time-out-spec.js

In addition to Mocha, you should test your code manually using Node.js. You can use the examples below at the bottom of the file run the file in Node.js.

Examples:

class Animal {
  constructor(age) {
    this.age = age;
  }

  growOlder() {
    this.age++;
    console.log(this.age);
  }
}

const dog = new Animal(1);
const cat = new Animal(5);

boundFuncTimer(dog, dog.growOlder, 5000); // in 5 seconds prints: 2
boundFuncTimer(cat, dog.growOlder, 7000); // in 7 seconds prints: 6