Array is empty after pushing items (synchronous)

Question

I am trying to read file from a .txt file in nodejs, when i get access to each line, I push it to an array but in the end, the array is empty.

var array=[];

  let lineReader = require('readline').createInterface({
    input: require('fs').createReadStream('file.txt')
  });
  
  lineReader.on('line', function (line) {
    console.log(line);
    array.push(line);
  });

console.log(array);

.Txt File Content

THIS IS LINE#1
THIS IS LINE#2
THIS IS LINE#3

Output

[]
THIS IS LINE#1
THIS IS LINE#2
THIS IS LINE#3

lineReader.on('line', function (line) {...}) is not synchronous ( mean, the function you pass to it is not called synchronously). — Felix Kling
– Felix Kling, Commented May 6, 2021 at 12:17
You say it's synchronous in the title...but an event listener (= on(...)) is not synchronous (as you can see in the output) — MrCodingB
– MrCodingB, Commented May 6, 2021 at 12:18

Ayzrian · Accepted Answer · 2021-05-06 12:27:02Z

1

The problem is that the thing happens async. You need to add a listener for close event.

lineReader.on("close", () => {
    console.log(array);
})

answered May 6, 2021 at 12:27

Ayzrian

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