How do you Get data from fs.readFile?

Question

function LoadMapFromText(route){

  var str = '';
  
  fs.readFile(route, (err, data) => {
    str = data.toString();
  });

  var pairs = str.split("-n");

  console.log(str);
}

ive been trying to fix this problem for god knows how long, and i just don't know how to do it. the string is not updating from inside the arrow function.

i already tried making the function async, and i already tried putting await before fs.readFile, but to no avail. i am at a loss of what to do.

readFile is async. use readFileSync for this purpose – Anil kumar Mar 05 '23 at 04:09 — Anil kumar, Mar 05 '23 at 04:09
Has absolutely nothing to do with the arrow function. – Dexygen Mar 05 '23 at 04:24 — Dexygen, Mar 05 '23 at 04:24

score -1 · Answer 1 · answered Mar 05 '23 at 04:11

The problem is that fs.readFile is an asynchronous function that implements a callback function. The callback function gets executed only after the file has been read. In your case, your "arrow function" is the callback function, which gets executed only after the file has been read. But by this time, the lines following the callback, including your console.log(str) statement, have already been executed.

Try using fs.readFileSync instead.

function LoadMapFromText(route){

  var str = fs.readFileSync(route, 'utf8');

  var pairs = str.split("-n");

  console.log(str);
}

score -1 · Answer 2 · answered Mar 05 '23 at 04:16

You should use the function fs.readFileSync() in the proposed case if it is a light file, otherwise you should use the callback of fs.readFile with a promise, so your string was not updated.

function LoadMapFromText(route){

  let str = '';
  
  str = String(fs.readFileSync(route))

  var pairs = str.split("-n");

  console.log(str, pairs);
}

How do you Get data from fs.readFile?

2 Answers2