javascript - returning undefined from readFile -

this question has answer here:

• how return response asynchronous call? 21 answers

i'm trying following code work:

'use strict';  var fs = require('fs');  var filename = 'readme.txt'; var str = fs.readfile(filename, 'utf8', function (err, data) {     if (err) {         console.log(err);         throw err;     }     return data; });  console.log('result read: ' + str); 

readme.txt:

console.log('working'); 

i'm trying display following:

result read: console.log('working'); 

readfile executed asynchronously, data can accessed inside callback function, if want synchronous, should use readfilesync

async:

'use strict';  var fs = require('fs');      var filename = 'readme.txt';     var str = fs.readfile(filename, 'utf8', function (err, data) {         if (err) {             console.log(err);             throw err;         }        console.log('result read: ' + data);     }); 

sync:

var str = fs.readfilesync(filename, 'utf8'); console.log('result read: ' + str);