fs append

1// Asynchronously:
2const fs = require('fs');
3
4fs.appendFile('message.txt', 'data to append', function (err) {
5  if (err) throw err;
6  console.log('Saved!');
7});
8
9// Synchronously:
10const fs = require('fs');
11
12fs.appendFileSync('message.txt', 'data to append');

1const fs = require('fs');
2
3fs.readFile('/Users/joe/test.txt', 'utf8' , (err, data) => {
4  if (err) {
5    console.error(err);
6    return
7  }
8  console.log(data);
9});

1const fs = require('fs');
2
3fs.appendFile('message.txt', 'data to append', function (err) {
4  if (err) throw err;
5  console.log('Saved!');
6});
7

1fs.readFile('filename', function read(err, data) {
2    if (err) {
3        throw err;
4    }
5    var content = data;
6  
7    console.log(content);  
8   
9});