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.