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小百科  ›  Node JS fs.readFile() Method - GeeksforGeeks
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    • In Node, the fs (File System) module provides a collection of methods for interacting with the file system. Among these methods, fs.readFile() stands out as a fundamental tool for reading data from files asynchronously. This article will delve into the fs.readFile() method, exploring its syntax, parameters, usage, and error handling.

    NodeJS readfile method

    The readfile method is used to asynchronously read the data from a file. It is a method of node js file system module . Asynchronously reading file content enables the non-blocking operation in Node.

    Syntax: 

    fs.readFile( file_path, encoding, callback_function )

    Parameters:

    The method accepts three parameters as mentioned above and described below:

    • file_path: It holds the file’s name to read or the entire path if stored at another location.
    • encoding: It holds the encoding of the file. Its default value is ‘utf8’ .
    • callback_function: A callback function is called after reading the file. It takes two parameters:
      • err: If any error occurred.
      • data: Contents of the file.

    Return Value:

    It returns the contents/data stored in file or error if any.

    If you’re looking to manage file operations efficiently in full-stack applications, the Full Stack Development with React & Node JS course provides detailed lessons on asynchronous file handling in Node.js.

    Steps to Create Node JS Application

    Step 1: In the first step, we will create the new folder by using the below command in the VScode terminal. 

    mkdir folder-name
    cd folder-name

    Step 2: Initialize the NPM using the below command. Using this the package.json file will be created. 

    npm init -y

    Project Structure:

    NodeProj

    Project Structure

    Example 1: Below examples illustrate the fs.readFile() method in Node JS. The output is undefined it means the file is null. It starts reading the file and simultaneously executes the code. The function will be called once the file has been read meanwhile the ‘readFile called’ statement is printed then the contents of the file are printed.

    JavaScript 
    //index.js
// Node.js program to demonstrate
// the fs.readFile() method
// Include fs module
var fs = require('fs');
// Use fs.readFile() method to read the file
fs.readFile('Demo.txt', 'utf8', function (err, data) {
    // Display the file content
    console.log(data);
console.log('readFile called');

    Step to run the Node App:
    

    node index.js
    Output: 
    

    readFile called
    undefined
    Example 2: Below examples illustrate the fs.readFile() method in Node JS:
    
            JavaScript
    
    //index.js
// Node.js program to demonstrate
// the fs.readFile() method
// Include fs module
const fs = require('fs');
// Use fs.readFile() method to read the file
fs.readFile('demo.txt', (err, data) => {
    console.log(data);

    Step to run the Node App:
    

    node index.js
    Output:
    

    undefined
    Error Handling
    When using fs.readFile(), it’s important to handle errors properly to prevent crashes and ensure graceful error recovery. Common errors include file not found, insufficient permissions, and I/O errors. You can handle errors by checking the err parameter passed to the callback function. If err is truthy, an error occurred during the reading process, and you should handle it accordingly.
    

    fs.readFile("example.txt", "utf8", (err, data) => {
        if (err) {
            if (err.code === "ENOENT") {
                console.error("File not found:", err.path);
            } else {
                console.error("Error reading file:", err);
            }
            return;
        }
        console.log("File content:", data);
    });
    Conclusion
    The fs.readFile method in Node.js provides a straightforward way to read file contents asynchronously. By understanding its syntax, parameters, usage, and error handling, you can effectively use it to read data from files in your Node.js applications. When working with file I/O operations, always remember to handle errors properly to ensure the reliability and stability of your applications.
    
                
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    Node.js filehandle.readFile() Method
    
                
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