Example of Asynchronous Nature of Node.js JavaScript

asyncExample.js

/**
 * Even though javascript doesn't have types, there are many
 * languages that people have built which complie to legitemate JS.
 * Check out TypeScript at http://www.typescriptlang.org/
 * For more information*/

/**
 * The output of this file is as follows:
  - Before myFun                                                                                                                                                                                                                                                                  
  - Value is : 6                                                                                                                                                                                                                                                                  
  - After myFun                                                                                                                                                                                                                                                                   
  - Value is : 7  
  */
  
var myFun = function(value, cb){
  value += 1; //value = 6
  
  process.nextTick(function(){ //nextTick -> place this function at the end of the event queue
    value += 1; //value = 7 but only when this function runs
      cb(value); 
  });
  
  cb(value); //immediately (synchronosly) call the callback, value still = 6
};

var callback = function(value){
  console.log("Value is : " + value);
};

//main
function main(){
  console.log("Before myFun");
  myFun(5, callback);
  console.log("After myFun");
}

main();