chaining.js

// Below is a drone object with six methods.
// Each method takes a callback and after some amount of time will execute that callback 
// For ease of testing, it will also console.log a value.

// At the bottom of the page the expected output is logged.
// We invoke the chained call of the drone object. 
// However the drone object does not yet have a chained api.

// Add a chained api to the drone object by only modifying the code in the middle of the page.

// A good answer should include the following criteria.
// 1. Code was only added between the below comments.
// 2. Each method in the chain executes only after the previous method has resolved
// 3. Your solution should be flexible to rearranging the methods or changing the timeouts.
// 4. Your solution should not change the behavior/side affects of the original methods. 

// You should assume that you don't know how the methods on the Drone object are implemented. 
// Only that they may or may not be asynchronous and and that they take a callback
// that will be called when the action is completed.

function Drone(){};

Drone.prototype.takeoff = function takeoff(callback) {
 setTimeout(function() {
   callback()
   console.log('Took off');
 }, 600);
};
Drone.prototype.turnOnCamera = function turnOnCamera(callback) {
 setTimeout(function() {
   callback()
   console.log('Camera turned on');
 }, 1000);
};
Drone.prototype.pointDownGimbal = function pointDownGimbal(callback) {
 setTimeout(function() {
   callback()
   console.log('Gimbal pointing down');
 }, 750);
};
Drone.prototype.flyToMission = function FlyToMission(callback) {
 setTimeout(function() {
   callback()
   console.log('Flown to mission');
 }, 2000);
};
Drone.prototype.takePhoto = function takePhoto(callback) {
 setTimeout(function() {
   callback()
   console.log('Photo taken');
 }, 500);
};
Drone.prototype.land = function land(callback) {
 setTimeout(function() {
   callback()
   console.log('Landed');
 }, 3000);
};
// DON'T MODIFY ANYTHING ABOVE HERE

// START ADD YOUR CODE HERE
var promise;
var  d  = new Drone()
var  drone = function(){
    this.takeoff =  function(){
      d.takeoff(function(){}) ;
   
     return this ;
    }
    this.turnOnCamera =  function(){
     
      d.turnOnCamera(function(){   })
     
     return this;
    }
    this.pointDownGimbal = function(){
     d.pointDownGimbal(function(){
       
      })
     return this;
    }
    this.flyToMission = function(){
     d.flyToMission(function(){
       
      })
     return this;
    }
    this.takePhoto = function(){
    promise = new Promise(function(resolve, reject){
     resolve({data: d.takePhoto(function(){ }) });

   });
     return this;
    }
     this.land = function(){
     d.land(function(){
       
      })
     return this;
    }
}

var drone = new drone()
// END ADD YOUR CODE HERE

//DONT MODIFY ANYTHING BELOW HERE
console.log("Expected Output:")
console.log("Took off");
console.log("Camera turned on");
console.log("Gimbal pointing down");
console.log("Flown to mission");
console.log("Photo taken");
console.log("Landed");

console.log("\n\nActual Output:")
drone.takeoff().turnOnCamera().pointDownGimbal().flyToMission().takePhoto().land();