27.7. Exercises: TypeScript

27.7.1. Part 0 - Get the Starter Code

  1. Login to your GitHub account.

  2. Fork the typescript-lc101-projects repository.

  3. Use the terminal to clone your fork from GitHub. If you need a reminder for how to do this, refer to the Git studio.

  4. Use the terminal to navigate into the typescript-lc101-projects folder, then into the exercises subfolder.

    $ ls
       typescript-lc101-projects
    $ cd typescript-lc101-projects
    $ ls
       exercises       studio
    $ cd exercises
    $ ls
       SpaceLocation.ts     parts1-5.ts    tsconfig.json
    

27.7.2. Part 1 - Declare Variables With Type

Run VSCode and open the typescript-lc101-projects folder. From the file tree, select the parts1-5.ts file.

VSCode file tree for the TypeScript exercises.

VSCode file tree

In the space indicated, declare and assign a variable for each of the following:

Variable Name Type Value
spacecraftName string 'Determination'
speedMph number 17500
kilometersToMars number 225000000
kilometersToTheMoon number 384400
milesPerKilometer number 0.621

27.7.3. Part 2 - Print Days to Mars

In the same file you opened in Part 1, do the following.

  1. Declare and assign these variables.
    1. Remember: variable declarations in TypeScript include the type!
    2. milesToMars is a number with the value of kilometersToMars * milesPerKilometer.
    3. hoursToMars is a number with the value of milesToMars / speedMph.
    4. daysToMars is a number with the value of hoursToMars / 24.
  2. Write a console.log statement that prints out the days to Mars.
    1. Use template literal syntax and the variables ${spacecraftName} and ${daysToMars}.
  3. Use the terminal in VSCode to compile your .ts file, then use the command node parts1-5.js to run the JavaScript file created during the build process.

Terminal

$ tsc parts1-5.ts
$ node parts1-5.js
   Determination would take 332.67857142857144 days to get to Mars.

27.7.4. Part 3 - Create a Function

  1. In the space indicated, define a function that calculates the days it would take to travel to a location.
    1. Function name getDaysToLocation
    2. Parameter
      • kilometersAway must be a number.
    3. Returns the number of days to a location.
      • Use the same calculations as in Part 2.1.
      • Inside the function, make the variable names generic. Use milesAway and hoursToLocation instead of milesToMars and hoursToMars.
      • The function should declare that it returns a number.
  2. Print out the days to Mars.
    1. Move the output statement from part 2 below your new function.
    2. Refactor the template literal to use ${getDaysToLocation(kilometersToMars)} and ${spacecraftName}.
  3. Print out the days to the Moon.
    1. Add another output statement and template literal using ${getDaysToLocation(kilometersToTheMoon)} and ${spacecraftName}.
  4. Use the terminal in VSCode to recompile your .ts file, then run the parts1-5.js file again.

Terminal

$ tsc parts1-5.ts
$ node parts1-5.js
   Determination would take 332.67857142857144 days to get to Mars.
   Determination would take 0.5683628571428571 days to get to the Moon.

27.7.5. Part 4 - Create a Spacecraft Class

Organize getDaysToLocation and the variables for name, speed, and miles per kilometer by moving them into a class.

  1. Define a class named Spacecraft.

    1. Properties
      • milesPerKilometer: number = 0.621;
      • name: string;
      • speedMph: number;
    2. Constructor
      • name is the first parameter and it MUST be a string.
      • speedMph is the second parameter and it MUST be a number.
      • Sets the class properties using this.name and this.speedMph.

    Note

    Once you complete the constructor, be sure to remove the variables you defined in part 1 (spacecraftName, milesPerKilometer, and speedMph.

  2. Move the function getDaysToLocation, defined in Part 3, into the Spacecraft class.

    1. Remember to place the function after the constructor.
    2. Update the function to reference the class properties this.milesPerKilometer and this.speedMph.
  3. Create an instance of the Spacecraft class.

    1. let spaceShuttle = new Spacecraft('Determination', 17500);
  4. Print out the days to Mars.

    1. Use template literals, ${spaceShuttle.getDaysToLocation(kilometersToMars)} and ${spaceShuttle.name}.
  5. Print out the days to the Moon.

    1. Use template literals, ${spaceShuttle.getDaysToLocation(kilometersToTheMoon)} and ${spaceShuttle.name}.
  6. Use the terminal in VSCode to recompile your .ts file, then run the .js file again.

Terminal

$ tsc parts1-5.ts
$ node parts1-5.js
   Determination would take 332.67857142857144 days to get to Mars.
   Determination would take 0.5683628571428571 days to get to the Moon.

27.7.6. Part 5 - Export and Import the SpaceLocation Class

  1. From the file tree in VSCode, open the SpaceLocation.ts file.

  2. Paste in the code provided below.

    1. Notice the export keyword. That is what allows us to import it later.
    1
    2
    3
    4
    5
    6
    7
    8
    9
    export class SpaceLocation {
       kilometersAway: number;
       name: string;
    
       constructor(name: string, kilometersAway: number) {
          this.name = name;
          this.kilometersAway = kilometersAway;
       }
    }
    
  1. Add the function printDaysToLocation to the Spacecraft class.

    1. Notice that it takes a parameter of type SpaceLocation.
    1
    2
    3
    printDaysToLocation(location: SpaceLocation) {
       console.log(`${this.name} would take ${this.getDaysToLocation(location.kilometersAway)} days to get to ${location.name}.`);
    }
    
  2. Import SpaceLocation into parts1-5.ts.

    1. Paste import { SpaceLocation } from './SpaceLocation'; to the top of parts1-5.ts.
  3. Replace the earlier console.log statements by using the class instance to print out the days to Mars and the Moon.

    47
    48
    spaceShuttle.printDaysToLocation(new SpaceLocation('Mars', kilometersToMars));
    spaceShuttle.printDaysToLocation(new SpaceLocation('the Moon', kilometersToTheMoon));
    
  4. Use the terminal in VSCode to compile your .ts file, then run the .js file again.

Terminal

$ tsc parts1-5.ts
$ node parts1-5.js
   Determination would take 332.67857142857144 days to get to Mars.
   Determination would take 0.5683628571428571 days to get to the Moon.

27.7.7. Sanity Check

The typescript-lc101-projects repository has two branches---master and solutions. 'Nuff said.