How to append JSON data to existing JSON file node.js

Try this. Don't forget to define anchors array.

var data = fs.readFileSync('testOutput.json');var json = JSON.parse(data);json.push(...anchors);fs.writeFile("testOutput.json", JSON.stringify(json))

I created two small functions to handle the data to append.

1. the first function will: read data and convert JSON-string to JSON-array
2. then we add the new data to the JSON-array
3. we convert JSON-array to JSON-string and write it to the file

example: you want to add data { "title":" 2.0 Wireless " } to file my_data.json on the same folder root. just call append_data (file_path , data ) ,

it will append data in the JSON file, if the file existed . or it will create the file and add the data to it.

data = {  "title":"  2.0 Wireless " }file_path = './my_data.json'append_data (file_path , data )

the full code is here :

   const fs = require('fs');   data = {  "title":"  2.0 Wireless " }   file_path = './my_data.json'   append_data (file_path , data )   async function append_data (filename , data ) {    if (fs.existsSync(filename)) {        read_data = await readFile(filename)        if (read_data == false) {            console.log('not able to read file')        }        else {            read_data.push(data)            dataWrittenStatus = await writeFile(filename, read_data)            if dataWrittenStatus == true {              console.log('data added successfully')            }           else{              console.log('data adding failed')            }        }      else{          dataWrittenStatus = await writeFile(filename, [data])          if dataWrittenStatus == true {              console.log('data added successfully')          }          else{             console.log('data adding failed')           }      }   }    async function readFile  (filePath) {      try {        const data = await fs.promises.readFile(filePath, 'utf8')        return JSON.parse(data)      }     catch(err) {         return false;      }    }    async function writeFile  (filename ,writedata) {      try {          await fs.promises.writeFile(filename, JSON.stringify(writedata,null, 4), 'utf8');          return true      }      catch(err) {          return false      }    }