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How to check for duplicates in a list and save each email one by line in a file

January 25, 2022

I have a list like this:

[
  'test@t-online.de',
  'kontakt@test.de',
  'info@test.de',
  'test@gmx.de',
  'kontakt@test.de',
]

I want to check for duplicates and save the list in a txt file with one email in each line. The final result would be in this case:

      test@t-online.de
      kontakt@test.de
      info@test.de
      test@gmx.de

fs.writeFileSync(‘./results/test.txt’, list)

How to do that?

>Solution :

Complete code. I have used "a" flag to append the data in same file

let fs = require('fs');

let data = [
    'test@t-online.de',
    'kontakt@test.de',
    'info@test.de',
    'test@gmx.de',
    'kontakt@test.de',
];
let stream = fs.createWriteStream("emails.txt", {'flags': 'a'});
stream.once('open', function(fd) {
    // this will remove duplicates from the array
    const result = data.filter((item, pos) => data.indexOf(item) === pos)
    result.forEach(email => stream.write(email + '\n'));
});