How to return empty array if file doesn't exists in NodeJS

Question

I would like to console.log a message and return an empty array if I try to read a file that doesn't exist. The getAllNotes function fires effective and the error is definitely thrown no such file or directory, open 'notes.json'.

However, why is the error thrown if I didn't specify throw err in my if statement? Secondly why doesn't my console.log message get outputted and the empty array not returned?

var getAllNotes = () => {
  console.log("MADE IT TO GET ALL NOTES")
  var notesArray = fs.readFileSync('notes.json', (err, data) => {
    if (err) {
      console.log("There are no notes to display");
      return [];
    } else {
      console.log("DATA",data)
      console.log("MADE IT TO PARSE")
      return JSON.parse(data);
    }
  });
  console.log("INSIDE GET ALL NOTES", notesArray)
};

c3st7n · Accepted Answer · 2017-04-26 08:01:12Z

2

fs.readFileSync is a blocking call and doesn't take a callback in the same way that fs.readFile does. It simply returns the contents of the file, see the below example:

var fs = require('fs');
var date = fs.readFileSync('myfile', 'utf8');
console.log(data);

When I ran your example an exception is thrown because you are providing a callback function where it is expecting a string or object for the options parameter.

You can do a blocking call with fs.existsSync(path) to check if the file exists before trying to read it.

Alternatively you can use the non-blocking version of the readFile and provide the callback as you were trying to do.

answered Apr 26, 2017 at 8:01

c3st7n

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2 Comments

Govind Rai Over a year ago

Oh my goodness. That fixed the problem. What a great learning opportunity... I would really like to know how you determined from reading the error message that it was expecting a string or object from the options parameter because I am rereading those errors and all I can take away is that the file I am trying to read doesn't exist.

c3st7n Over a year ago

So all I did was copy your example, add the require for fs and add a line to call your getAllNotes(). When I then ran this with nodejs I got this exception: TypeError: Expected options to be either an object or a string, but got function instead. Are you running it in the same way?

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