fs - w3toppers.com

How to close a readable stream (before end)?

Edit: Good news! Starting with Node.js 8.0.0 readable.destroy is officially available: https://nodejs.org/api/stream.html#stream_readable_destroy_error ReadStream.destroy You can call the ReadStream.destroy function at any time. var fs = require(“fs”); var readStream = fs.createReadStream(“lines.txt”); readStream .on(“data”, function (chunk) { console.log(chunk); readStream.destroy(); }) .on(“end”, function () { // This may not been called since we are destroying the stream // … Read more

Using filesystem in node.js with async / await

Native support for async await fs functions since Node 11 Since Node.JS 11.0.0 (stable), and version 10.0.0 (experimental), you have access to file system methods that are already promisify’d and you can use them with try catch exception handling rather than checking if the callback’s returned value contains an error. The API is very clean … Read more

Write / add data in JSON file using Node.js

If this JSON file won’t become too big over time, you should try: Create a JavaScript object with the table array in it var obj = { table: [] }; Add some data to it, for example: obj.table.push({id: 1, square:2}); Convert it from an object to a string with JSON.stringify var json = JSON.stringify(obj); Use … Read more

Check synchronously if file/directory exists in Node.js

The answer to this question has changed over the years. The current answer is here at the top, followed by the various answers over the years in chronological order: Current Answer You can use fs.existsSync(): const fs = require(“fs”); // Or `import fs from “fs”;` with ESM if (fs.existsSync(path)) { // Do something } It … Read more

How to append to a file in Node?

For occasional appends, you can use appendFile, which creates a new file handle each time it’s called: Asynchronously: const fs = require(‘fs’); fs.appendFile(‘message.txt’, ‘data to append’, function (err) { if (err) throw err; console.log(‘Saved!’); }); Synchronously: const fs = require(‘fs’); fs.appendFileSync(‘message.txt’, ‘data to append’); But if you append repeatedly to the same file, it’s much … Read more

How to download a file with Node.js (without using third-party libraries)?

You can create an HTTP GET request and pipe its response into a writable file stream: const http = require(‘http’); // or ‘https’ for https:// URLs const fs = require(‘fs’); const file = fs.createWriteStream(“file.jpg”); const request = http.get(“http://i3.ytimg.com/vi/J—aiyznGQ/mqdefault.jpg”, function(response) { response.pipe(file); // after download completed close filestream file.on(“finish”, () => { file.close(); console.log(“Download Completed”); }); … Read more

Writing to files in Node.js

There are a lot of details in the File System API. The most common way is: const fs = require(‘fs’); fs.writeFile(“/tmp/test”, “Hey there!”, function(err) { if(err) { return console.log(err); } console.log(“The file was saved!”); }); // Or fs.writeFileSync(‘/tmp/test-sync’, ‘Hey there!’);