3. Reading and Writing Files in Node.js

Node.js provides the fs (File System) module to interact with the file system for reading and writing files.
It includes both asynchronous and synchronous methods for working with files

Reading Files

Synchronous File Reading
- readFileSync is the synchronous method for reading files, it only takes the file location and the file encoding
- This will block code execution until the file has been read
- In applications where performance is critical, it’s often preferred to use the asynchronous version, but the synchronous version can be a lot easier to reason about
- Example
  const data = fs.readFileSync('example.txt', 'utf8'); console.log(data);
  - This will block the code until the entire contents of example.txt are read, and then print out the contents.
Asynchronous File Reading
- readFile is the asynchronous method for reading files, it take the file location and encoding, same as the synchronous method. However, it also takes a callback function which will be ran after the file contents are read
- The callback function takes two parameters when it is ran, an Error object (in case an error occurs while reading) and a string containing the file contents
- Example
```
fs.readFile('example.txt', 'utf8', (err, data) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(data);
});
```
- This will not block the code, but when the reading of example.txt has finished, the data will be printed or the error (if applicable)

Synchronous File Writing
- writeFileSync (like readFileSync) is the synchronous method for writing files
- Again, it will block execution until the file has been written and it is often preferred to use the asynchronous version if performance is an issue
Asynchronous File Writing
- Simular to readFile the asyncrhonous counterpart for writing is writeFile
- writeFile also takes a callback function (like it’s readFile counterpart), however this callback only takes an error parameter, as there is no data to return

When working with files, there are many opportunities for error
It’s important to be aware of this, and do your best to handle at least some of the common errors
File not found: An extremely common error that occurs when the file attemtping to be read, or written to, does not exist.
- Surrounding any particular code in a try/catch block can help
- You can also check if a file exists with something like existsSync
Inadequate permssions: Another common errors that occurs when you don’t have the proper permissions to perform the asked file operation
- The best method for this error is to use standard error handling like a try/catch statement or checking the error object in the async callback