CODEWITHSUNDEEP
javascriptnode.jsfunctionconsole
Christopher Allen
Christopher Allen

Reputation: 8589

fs.readFile Function Response is undefined... Any Ideas?

Im running a simple readfile command, for a video tutorial, and this is the code exactly as the instructor saved it...

var fs = require("fs");
console.log("Starting");
fs.readFile("./sample.txt", function(error, data) {
console.log("Contents: " + data);
});
console.log("Carry on executing");

i have the sample.txt in the same folder as this js file, and in the sample.txt file i have "This is a sample output for this text document", unfortunately i get a "undefined" as the output for the data variable in the code.

If anybody has any insight as to why this is happening, it would be wonderful if someone would help....

THANKS

Upvotes: 4

Views: 11352

Answers (3)

Suhail Abdul Rehman Chougule
Suhail Abdul Rehman Chougule

Reputation: 2869

Even when the file exists Why Does fs.readFile() function of Node.js always returns undefined only when console.log(data) is used it shows value. Example below 

    var content
    function myReadFile(filepath){
    fs.readFile(filepath,'utf8', function read(err, data) {
    if (err) {
      throw err;
    }
    content = data
    console.log(content); // Only this part of it returns the  value 
                          // not the content variable itself 
    })
    return content;
    }

Upvotes: 1

Thorsten Lorenz
Thorsten Lorenz

Reputation: 11847

Depending on where you are running this from, the root at which ./sample.txt gets resolved may vary.

To ensure, that it resolves relative to your module, do the following:

var fs = require("fs");
var path = require('path');

var sampleTxt = path.join(__dirname, 'sample.txt');

console.log("Starting");
fs.readFile(sampleTxt, function(error, data) {
  if (error) return console.error(error);
  console.log("Contents: " + data);
});
console.log("Carry on executing");

Upvotes: 3

Riwels
Riwels

Reputation: 786

Try checking if the file exists first:

var fs = require("fs");
console.log("Starting");

fs.exists("./sample.txt", function(fileok){
  if(fileok)fs.readFile("./sample.txt", function(error, data) {
    console.log("Contents: " + data);
  });
  else console.log("file not found");
});
console.log("Carry on executing");

If it doesn't exists, check the path, filename and extension, because your code is OK.

Upvotes: 5

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