File Reader Challenge

Create a Node.js app that reads from a text file and manipulates the data. This challenge illustrates the need for callbacks, because the fs module requires a callback to receive the data from a file!

Examples

Review the examples here before starting the challenge. Note how fs.readFile works.

Setup (Repl.it)

1. Create a new Node.js Repl Project
2. In the new project, create a file named .replit
3. In the .replit file, add the following text:

    run = "node FileReader.js"
   

Creating Files

1. Create a new text file named TextInfo.txt
2. Edit TextInfo.txt so it contains some interesting text
3. In the same folder as TextInfo.txt, create a new JavaScript file named FileReader.js

Preparing to Read Files

Open the FileReader.js file for editing.

1. At the top of the file, use the following command to include the File System module

    const fs = require('fs');
   

2. Underneath the require, define a new function named yellFile
3. The yellFile function should take two parameters: error and dataString
   • For now, simply use console.log in the body of the yellFile function to say "here"
4. Underneath the yellFile function definition, use fs.readFile to read the text file
   • The path argument should be 'TextInfo.txt'
   • The options argument should be 'utf-8'
   • The callback argument should be yellFile
5. Run the code and make sure "here" appears!

Yelling the File Contents

The yellFile function should take the contents of the text file (as long as it can successfully open the file), and display them to the user in all caps.

1. Remove the console.log from the body of the yellFile function
2. If there is an error (stored in the error parameter) reading the file, display a message to the user using console.error
3. If there is NOT an error, convert text from the file (stored in the dataString parameter) to all uppercase
4. Display the uppercase text to the user with console.log
5. Run the code to see the text file contents in all caps!

Elmer Fudd Translator

Define a new function named elmerFudd that takes a string and converts it to "Elmer Fudd Speak." Take a look at funtranslations.com/fudd to see it in action. The translation should apply the following changes to the text:

• Replace every 'th' with a 'd'
• Replace every 'r' with a 'w'
• Replace every 'l' with a 'w'

Use the elmerFudd function in the fs.readFile call to hook it up to the text file!

Writing a File Translation

Reference: https://nodejs.dev/learn/writing-files-with-nodejs

Use fs.writeFile to write the file translation into a new file. After the file has been successfully written, write a message to the console telling the user the operation was successful.

Dealing with User Input

Reference: https://nodejs.org/api/readline.html

Use the readline module to receive input from the user. Ask the user for the following information:

• Path to the file to read
• Path to the file to write
• Which function to perform (yelling or Elmer Fudd translation)

Then, use the information the user enters to execute the program.