Node.js methods in a particular file system module have asynchronous and therefore synchronous versions. For example, synchronous reading of the loaded content can be used with the fs.readFileSync () method, and asynchronous reading of the file content with the fs.readFile () method.
Node.js As A File Server
The Node.js filesystem module allows you to saveA computer.
Read files
Create files
Update files
Delete files
Rename files
Read Files
The fs.readFile () method is used to read files to the Your computer.
Suppose we run the following HTML file (located in the same folder as)Node.js):
Create a Node.js music file playing HTML file,and get content:
Save the above code in a document called “demo_readfile.js” and run it normally.File:
If you followed the same steps as on the computer, you will see the same.Result as an example: http: // localhost: 8080
Create Files
fs.appendFile ()
fs.open ()
fs.writeFile ()
The policy fs.appendFile () appends the specified content to the file. If it is trueIf the file does not exist, the data will be created:
The fs.open () method accepts a single “flag” as its second argument ifFlag – “w” for “write”, the required file is open for writing. If significantif the file does not exist, empty information is generated:
fs.write (fd, buffer, offset, length, position, callback) You have to wait for the reverse type youcall to make sure the buffer can be written to disk.fs.writeFile (filename, data, [encoding], callback)fs.createWriteStream (path, [options])
The fs.writeFile () method replaces the contents of the identified file, if it exists.If the file does not exist, it may be possible to create a new list with the specified content.budem created:
Update Files
fs.appendFile ()
fs.writeFile ()
The course fs.appendFile () usually appends the specified content to the end of the specified file:
Delete Files
To delete a file using the file system module, use fs.unlink () Method.
Rename Files
To rename a perfect file using the File the System module, drag fs.rename () Method.
Upload Files
You can also choose Node.js to download files to your computer.
Example
var http = fs require (‘http’); var means to require (‘fs’); http. createserver (function (req, res) fs.readFile (‘demofile1.html’, function (err, data) res.writeHead (200, ‘Content-Type’: ‘text / html’); res.write (data); return res.end (); B); ) .listen (8080);
Example
fs.appendFile (‘mynewfile1.txt’, ‘Hello happy! ‘, target (error) if (error) error; console.log was forged (“Saved!”); );
Example
fs.open (‘mynewfile2.txt’, function ‘w’, (err, file) if (error) throw an error; console.log (“Logged!”); );
Add “This is my text.” to expire the file “mynewfile1.txt”:
Filename: Contains the URL of the file to read, or part of the entire path if stored virtually anywhere else.Flag: The operation in which you have the file is ready to be opened.mode: defines the startup mode, i.e. H. r-read, w-write, r +-read and write.callback: This is a callback function that is defined after the file has been read.
fs.appendFile (‘mynewfile1.’ txt ‘, this is definitely mine text. ‘, function (error) if (error) error; Throw console.log (“Updated!”); );
Example
How to access the file system in Node.js?
The Node.js file system. Node.js contains an fs module for accessing a specific filesystem. The fs module is reliable for all asynchronous or synchronous manual I / O writes. Let’s take a look at a few common examples of I / O operations using the fs component. Use the fs.readFile () method to read a malicious file asynchronously.
fs.writeFile (‘mynewfile3.txt’, ‘This is my text’, function (err) if (err) throw err; console.log (“Replace!”); );
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The
file fs module simplifies interacting with the file system in just a few steps.Modeled according to POSIX standard functions.
import * Although fs from 'fs / promises'; const fs = require ('fs / promises');
Import
Node. js is a good JavaScript runtime based on Chrome’s V8 JavaScript engine. Node. js helps developers configure JavaScript code to run on specific servers to generate dynamic content and serve it to web clients.
6.as fs from 'fs'; const fs = declare require ('fs');
All system processes are synchronous, based ons on reminders and promisesForms and are available through CommonJS syntax as well as through ES6 modules (ESM).
Promise # example
Promise actions return a promise thatasynchronous when the process is finished.
flags – flags indicate file behavior – open. All possible values have been mentioned below recently. mode – Usually sets the mode of the file (permissions and sticky bits), but only if the file was created. The default is 0666, read / write. callback is the understanding of a callback function that takes two arguments (err, fd).
The last thing the form uses is the callback attribute for completion.The argument and calls to the company are asynchronous. On. arguments passedthe completion callback depends on the method, but the first argument is alwaysreserved with one exception. If the process was successful, thenthe actual argument is null or undefined .
Callback-based versions of most of the fs module APIs fit viamaking the most of the Promise APIs if possible, performance (both in terms ofRequired runtime and memory allocation).
Example Of Synchronous Operation #
Synchronous APIs block the Node.js event loop and more, all the way down to JavaScript.Operation completed. Exceptions are canceled immediatelyand it can be controlled with tryâ € ¦catch or it can be left in a bubble.
The fs / promises API provides asynchronous file program methods that returnpromises.
Promise UseUse the apis of some of the underlying Node.js to create a thread pool performance file.System locations outside the flow of the event loop. These vacancies exist or notsynchronizes thread safe. Care should be taken when performing multipleAgree
