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Node.js exercises

Show the current time

Write a now.mjs script that prints the current date and time to your console when executed:

$> node now.mjs
Tue Sep 15 2022 11:00:31 GMT+0200 (Central European Summer Time)

List the current directory

Write a list.mjs script that lists the contents of the directory where it is executed. Here's how the output could look like, but of course it will depend on what files are on your machine and which directory you list:

$> node list.mjs
Applications Documents Downloads Music ...

$> cd Downloads

$> node list.mjs
cat.jpg more-cats.png

Bonus: update the script so that it ignores "hidden" files following the Unix convention (i.e. files with a name starting with a "dot" . character are hidden):

$> ls -a
. .. some-file.txt .hidden-file

$> node list.mjs
some-file.txt

Hint: if you don't have any directory with hidden files, you can easily create an empty hidden file with the command touch .hidden-file.

Calculator

Save the following contents to a file named calculate.mjs:

import { add, multiply } from './calculator/simple.mjs';
import { pow } from './calculator/advanced.mjs';

console.log(`2 added to 1 is: ${add(1, 2)}`);
console.log(`2 multiplied by 3 is: ${multiply(2, 3)}`);
console.log(`2 to the power of 10 is: ${pow(2, 10)}`);

Write the missing files so that the following command works:

$> node calculate.mjs
2 added to 1 is: 3
2 multiplied by 3 is: 6
2 to the power of 10 is: 1024

You may find the Math.pow function helpful.

Notoriously psychedelic modules

Write a unique.mjs script which takes any number of arguments and prints each unique argument on one line.

Use the Lodash library to accomplish this. The goal of this exercise is to install and use a third-party library that is not provided out of the box with Node.js, using the npm package manager.

The resulting script should behave like this:

$> node unique.mjs 1 2 4 3 2 3 5 6 4 4
1
2
4
3
5
6

$> node unique.mjs Hello Bob Hello Alice
Hello
Bob
Alice

You could of course implement the detection of unique values yourself, but that is not the purpose of this particular exercise.

To complete this exercise:

  • Install Lodash.
  • Find the appropriate Lodash function.
  • Write your script.

You may find the following documentation useful:

Yell

Create a Node.js command line script named yell.mjs which:

  • Takes one file name as an argument.
  • Reads the file with the UTF-8 encoding.
  • Converts the contents of the file to uppercase.
  • Outputs the converted contents.

The expected behavior should be:

$> cat rainbow.txt
Somewhere over the rainbow
Way up high
...

$> node yell.mjs rainbow.txt
SOMEWHERE OVER THE RAINBOW
WAY UP HIGH
...

Here's some text you may save to the file rainbow.txt:

Somewhere over the rainbow
Way up high
There's a land that I heard of
Once in a lullaby

Somewhere over the rainbow
Skies are blue
And the dreams that you dare to dream
Really do come true

Someday I'll wish upon a star
And wake up where the clouds are far
Behind me
Where troubles melt like lemon drops
Away above the chimney tops
That's where you'll find me

Somewhere over the rainbow
Bluebirds fly
Birds fly over the rainbow
Why then, oh why can't I?

If happy little bluebirds fly
Beyond the rainbow
Why, oh why can't I?

You may find the following documentation useful: