hybrid function

sync-async-hybrid.js

var fs = require('fs');
const cache = {};

function readFile(fileName, callback) {
    if (cache[fileName]) {
        return callback(null, cache[fileName])
    }
    fs.readFile(fileName, (err, fileContent) => {
        if (err) {
			console.log(err);
			return callback(err);
		}
        cache[fileName] = fileContent;
        callback(null, fileContent);
    });
}	
function letsRead(){
  readFile('multi.js', (err, result) => {
    // error handler redacted
    console.log('file read complete');
  });

  console.log('file read initiated')
}

letsRead()	
setTimeout(() => {
       letsRead()		
   }, 1000);