node.js code to append data to a file

Question

How can I append data to a file using node.js

I already have a file named myfile.json with data. I want to check if the file name exists and then append some data to that file.

I'm using following code

var writeTempFile = function (reportPath, data, callback) {   
    fs.writeFile(reportPath, data, function (err) {
        //if (err) //say(err);
        callback(err);
    });
}
writeTempFile(reportDir + '_' + query.jobid + ".json", data, function (err) {
    context.sendResponse(data, 200, {
        'Content-Type': 'text/html'
    });

There is one issue: You can't truly append data to a file of JSON format while preserving the format. You would have to read the data, parse it as JSON, edit the JSON and add your data, and then write the JSON back to the file. — Munim
– Munim, Commented Jan 23, 2014 at 5:12
It really depends on your JSON structure and what data you are trying to append. — Munim
– Munim, Commented Jan 23, 2014 at 6:34

Ali · Accepted Answer · 2014-01-23 05:35:52Z

1

You can use jsonfile

var jf = require('jsonfile');
var yourdata;
var file = '/tmp/data.json';
jf.readFile(file, function(err, obj) {
    if(!err) {
        var finalData = merge(obj, yourdata);

        jf.writeFile(file, finalData, function(err) {
            console.log(err);
        });
    }
});

You need to implement your merging logic in merge(object1, object2)

https://npmjs.org/package/jsonfile

answered Jan 23, 2014 at 5:35

Ali

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Comments

mjkaufer · Accepted Answer · 2014-01-23 05:10:39Z

0

Check out the following code.

function addToFile(reportPath, data, callback){
    fs.appendFile(reportPath, data, function (err) {
        callback(err);
    });
}

answered Jan 23, 2014 at 5:10

mjkaufer

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1 Comment

Sush Over a year ago

iam getting this error` fs.appendFile(reportPath, data, function (err) ^ TypeError: Object #<Object> has no method 'appendFile' `

NarendraSoni · Accepted Answer · 2014-01-23 05:25:14Z

0

Node offers fs module to work with file system. To use this module do

var fs = require('fs')

To append some data to file you can do:

fs.appendFile('message.txt', 'data to append', function (err) {
  if (err) throw err;
 console.log('The "data to append" was appended to file!');
});

Node offers you both synchronous and asynchronous method to append data to file, For more information please refer to this documentation

answered Jan 23, 2014 at 5:25

NarendraSoni

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5 Comments

Sush Over a year ago

am getting TypeError: Object #<Object> has no method 'appendFile'

Munim Over a year ago

@Sush you might be using an old version of Node.js if you are getting that error.

Sush Over a year ago

my node version is v0.6.12

oliverseal Over a year ago

Purely a guess, but I think a lot of the fs stuff changed around 0.9ish. Prior to that it has a lot of cross-platform issues (not to say that it's void of them now). It's on v0.10.24 now.

NarendraSoni Over a year ago

@Sush use nvm to upgrade it to the latest. It should be working after that.

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