As we know, reading the content of a file is one of the most common and important tasks of programming. Let's take a look at how we can read files in node.js.

Using readFile():

readFile takes three parameters, and they are:

path: Filepath of the file to read
encoding: It is an optional parameter; possible values are ascii, utf8,and base64.
callback: It is passed with two arguments: error and data,error contains the error message, and data contains the data coming from the file.
readFile is asynchronous in nature; therefore, it will not interrupt the execution of the program.

//importing file system module 
const fs=require('fs')
const path='./myFiles/read.txt'
fs.readFile(path,'utf8',(err,data)=>{
    if(err)return console.log("error occured while reading data");
    console.log(data);
})

output in the console is as shown below

Hello from read.txt

without 'utf8' encoding then output will be raw buffer data

<Buffer 48 65 6c 6c 6f 20 66 72 6f 6d 20 72 65 61 64 2e 74 78 74>

using readFileSync():

readFileSync takes two parameters, and they are:

path: Filepath of the file to read
encoding: It is an optional parameter; possible values are ascii, utf8,and base64.

readFileSync is synchronous in nature, which means the rest of the code execution will be stopped until the file is read completely.

//importing file system module
const fs = require("fs");
const path = "./myFiles/read.txt";
try {
  const data = fs.readFileSync(path, 'utf8');
  console.log(data);
} catch (err) {
  console.error(err);
}

output in the console is as shown below

Hello from read.txt

Using promise-based readFile():

Promise-based readFile takes two parameters, and they are:

path: Filepath of the file to read
encoding: It is an optional parameter; possible values are ascii, utf8,and base64.

since it is promise-based we can use async-await.

//importing promise-based file system module
const fsPromise = require("fs").promises;
const path = "./myFiles/read.txt";

const fileRead = async () => {
  try {
    const data = await fsPromise.readFile(path, "utf8");
    console.log(data);
  } catch (err) {
    console.error(err);
  }
};

fileRead();

output in the console is as shown below

Hello from read.txt