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

Question

How to append an existing JSON file with comma "," as separator
anchors = [ { "title":" 2.0 Wireless " } ]
fs.appendFileSync('testOutput.json', JSON.stringify(anchors));
This current code's output is like this
[
{
"title":" 2.0 Wireless "
}
]
[
{
"title":" Marshall Major II "
}
]
How to I get this in the correct format with comma "," as separator
I want to get something like this
[
{
"title":" 2.0 Wireless "
},
{
"title":" Marshall Major II "
}
]

Answer 1

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))

Answer 2

I created two small functions to handle the data to append.
the first function will: read data and convert JSON-string to JSON-array
then we add the new data to the JSON-array
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
}
}