Node.js file system CRUD

const isExist = require("fs"); const PATH = `./people.json`; // This could be rewritten using fsPromises Class as promisified version of check whether file exists or not : // @https://nodejs.org/api/fs.html#fspromisesaccesspath-mode isExist.access(PATH, isExist.F_OK, async (err) => { if (err) { console.error(`File by the name of ${PATH} has not existed ; ${PATH} was created .`); const dummy_content = `[{"id": 0, "db_engine" : "MOCKED_mongoDB", "metadata": "some_metadata", "filename": "${PATH}"}]`; try { await isExist.writeFile( PATH, dummy_content, {flag : "w+" /* r+ would throw an error !*/} , dummy_res => dummy_res /* ? res : console.info("Dummy async operation done!") */); } catch (err) { console.error(err) } } else { console.log(`File of ${PATH} already exists`); }; }); 

const fs = require("fs"); const fsPromises = require("fs").promises; const PATH = `./people.json`; async function main(){ let f1 = await (fsPromises.readFile(PATH, {encoding: "utf-8"})); console.log( "current files content is: ", f1 ); // Reading the file before inserting (appending) something new may take some time , that's why hereby we strongly should use fsPromise over synchronous fs Class let file_descriptor = null; try { /* must explicitly change default flag of "r" to sth like "r+" ! : @https://nodejs.org/api/fs.html#fs_file_system_flags */ file_descriptor = await fsPromises.open(PATH, "r+"); // let's assign a value to the file of people.json as file descriptor (fd) console.log("file_handle_descriptor reference: ", file_descriptor.fd); /* (^see below for caret) hereby file_descriptor.fd technically equals to 3 , yes simply No. 3 */ console.log({filehandleBuffer : file_descriptor}) } catch(file_descriptor_error) { console.error(file_descriptor_error); } // Signature of : <Buffer 00 00 00 00 00> where as each pair of 00 called "hex dump" ; Each byte (8 bits) is represented as a two-digit hexadecimal number [@wikipedia.org] let YOUR_CONTENT = ',{"id": 1, "new_data": "CRUD 123"}]'; // your content wished to be appended (inserted) console.log("YOUR_CONTENT_LENGTH: ", YOUR_CONTENT.length) /* Signature of fs.write() : isExist.write(fd, buffer, offset [of buffer given], Buffer.alloc(length, whereas each byte presented in duplex of hex dump), position [at file start writing], (err, bytesWritten, buffer)=>{return;} | (err, stringWritten, string)=>{return;}) */ fs.write(file_descriptor.fd, Buffer.from(YOUR_CONTENT), 0, null, f1.length-1, (err, bytesWritten, buffer)=>{ if (err) {throw err;} else { console.log("bytesWritten: ", bytesWritten); console.log("buffer: ", buffer); } }); // return; } main(); 

const fsPromises = require('fs').promises; async function main(){ let f1 = await (fsPromises.readFile('./people.json', {encoding: "utf-8"})); console.log( "current files content is: ", Array.isArray(JSON.parse(f1))); let f1Parsed = JSON.parse(f1); let temp = []; f1Parsed.forEach((value, index)=>{ temp.push({index : value}) }); console.log("temp before delete: ", temp); temp.forEach((val, inx)=>{ if( temp.find((obj) => obj.index.id && inx === 1) ) { delete temp[inx]; } }); console.log("temp after delete: ", temp); await fsPromises.writeFile('./people.json', JSON.stringify(temp)); // return; } main() 

const fsPromises = require('fs').promises; const PATH = './people.json'; async function remove(){ try{ await fsPromises.unlink(PATH); console.info(`File by the name of ${PATH} was deleted`); } catch(err){ console.error(err, `File by the name of ${PATH} does not exist ; TIP: Run node CREATE.js on Shell first`); } // return; } remove()