How to do it...

1. Open your command-line application and navigate to your workspace.
2.  Create a new folder named 3-08-simulating-finally.
3. Copy or create an index.html that loads and runs a main function from main.js.
4. Create a main.js file with a main function that logs out messages for before and after promise creation:

export function main() { 
 
  console.log('Before promise created'); 
 
  console.log('After promise created'); 
} 

5. Create a function named addBoosters that throws an error if its first parameter is false:

function addBoosters(shouldFail) { 
  if (shouldFail) { 
    throw new Error('Unable to add Boosters'); 
  } 
 
  return { 
    boosters: [{ 
      count: 2, 
      fuelType: 'solid' 
    }, { 
      count: 1, 
      fuelType: 'liquid' 
    }] 
  }; 
} 

6. Use Promise.resolve to pass a Boolean value that is true if a random number is greater than 0.5 to addBoosters:

export function main() { 
 
  console.log('Before promise created'); 
 
  Promise.resolve(Math.random() > 0.5)
    .then(addBoosters) 
 
  console.log('After promise created'); 
} 

7. Add a then function to the chain that logs a success message:

export function main() { 
 
  console.log('Before promise created'); 
  Promise.resolve(Math.random() > 0.5) 
    .then(addBoosters) 
       .then(() => console.log('Ready for launch: ')) 
 
  console.log('After promise created'); 
} 

8. Add a catch to the chain and log out the error if thrown:

export function main() { console.log('Before promise created'); Promise.resolve(Math.random() > 0.5) .then(addBoosters) .then(() => console.log('Ready for launch: ')) .catch(console.error) console.log('After promise created'); }

9. Add a then after the catch, and log out that we need to make an announcement:

export function main() { console.log('Before promise created'); Promise.resolve(Math.random() > 0.5) .then(addBoosters) .then(() => console.log('Ready for launch: ')) .catch(console.error)
.then(() => console.log('Time to inform the press.')); console.log('After promise created'); }

10. Start your Python web server and open the following link in your browser: 
    http://localhost:8000/.
11. If you are lucky and the boosters are added successfully, you'll see the following output:

12. If you are unlucky, you'll see an error message like the following: