asynchronous Getting started with asynchronous File Reading in Node js

Example

      var fs = require("fs");
      fs.readFileSync(‘abc.txt’,function(err,data){ //Reading File Synchronously
      if(!err) {
      console.log(data);
      }
      //else
      //console.log(err);  
      });
      console.log("something else");

Here, the program was waiting while reading the file. It will not go further before completing the read operation, which is an example of blocking code. But ideally, we should proceed further while the program was reading the file and once it is done we should go back and process that. That is what happening in the following code.

    var fs = require("fs");
    fs.readFile(‘abc.txt’,function(err,data){//Reading file Asynchronously
    if(!err) {
    console.log(data);
    }
    });
    console.log("something else");

Here, the program is not waiting, hence you see the console first and file contents later.