Nodejs saving file linebreak dosent work on initial run - node.js

Question

I am trying to generate a list of links inside <fileName.txt> file like this:
fs.writeFile(fileName, linksRemaining, function(err){
But if the file already exists I want to continue adding links without over-writing old ones. So I simply check if it exists store the data in a variable and add the additional content after a line break. like this:
fs.exists(doneFileName, function(exists) {
if (exists) {
fs.readFile(doneFileName, 'utf8', function (err, data) {
if(!err){
linksCurrentDoneList = data;
linksCurrentDoneList = linksCurrentDoneList+'\n'+linkTarget;
callback(1);
}else{
return console.log("Error: "+err);
}
});
....
The above code is in a loop and puts links several time, Issues is that on first run of my loop it negates line break '\n' but on 2nd and so on loops it works...
Suppose I am running loop for three links at a time, the result will be like this in notepad:
http://www.link1.com/
http://www.link2.com/
http://www.link3.com/http://www.link4.com/
http://www.link5.com/
http://www.link6.com/http://www.link7.com/
http://www.link8.com/
http://www.link9.com/http://www.link10.com/
http://www.link11.com/
.....
What I am trying to achieve is quite obvious... a line break for each link -- I am completely out of clue why is this happening,
In frustration I tried the following:
linksCurrentDoneList = '\n'+linksCurrentDoneList+'\n'+linkTarget+'\n';
But didn't help, in fact the line break was still just 1(same as the example above). Any one have any clue what might be going on?
EDIT:
Every link is on a separate line if I open my .txt file in another software like ms-world !!.

Answer 1

Seems like you want to use append function to append data to a file.
var fs =require('fs');
fs.appendFile('test.txt', "This is a test.\n", {flag: 'a'}, function(err) {
if (err) throw err;
console.log('The data was appended to file!');
});
Note that if test.txt doesn't exist, appendFile() will create. Here is he output running 2 times:
This is a test.
This is a test.