The following code outputs the content of the index.html (it just contains the text hello world) to the browser. However, when I replace readFile()
with readFileSync()
, the request times out.
What am I missing? Is a different kind of buffer required? I am using node 0.61 and express 2.4.
var express = require('express');
var fs = require('fs');
var app = express.createServer(express.logger());
app.get('/', function(request, response) {
fs.readFile('index.html', function(err, data){
response.send(data.toString());
});
});
var port = process.env.PORT || 5000;
app.listen(port, function() {
console.log("Listening on " + port);
});
This question is related to
javascript
node.js
express
readFileSync()
is synchronous and blocks execution until finished. These return their results as return values.
readFile()
are asynchronous and return immediately while they function in the background. You pass a callback function which gets called when they finish.
let's take an example for non-blocking.
following method read a file as a non-blocking way
var fs = require('fs');
fs.readFile(filename, "utf8", function(err, data) {
if (err) throw err;
console.log(data);
});
following is read a file as blocking or synchronous way.
var data = fs.readFileSync(filename);
LOL...If you don't want
readFileSync()
as blocking way then take reference from the following code. (Native)
var fs = require('fs');
function readFileAsSync(){
new Promise((resolve, reject)=>{
fs.readFile(filename, "utf8", function(err, data) {
if (err) throw err;
resolve(data);
});
});
}
async function callRead(){
let data = await readFileAsSync();
console.log(data);
}
callRead();
it's mean behind scenes
readFileSync()
work same as above(promise) base.
'use strict'
var fs = require("fs");
/***
* implementation of readFileSync
*/
var data = fs.readFileSync('input.txt');
console.log(data.toString());
console.log("Program Ended");
/***
* implementation of readFile
*/
fs.readFile('input.txt', function (err, data) {
if (err) return console.error(err);
console.log(data.toString());
});
console.log("Program Ended");
For better understanding run the above code and compare the results..
Source: Stackoverflow.com