Submitting Async Node assignment

.gitignore

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+
+
+
+
+node_modules/

README.md

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 # assignment_async_nodejs
 Async Node.js sprint
+Hi.. This is Lakshmi Maduri

data/lorem.txt

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+Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod.
+
+

data/write_here.txt

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+hello

emitter.js

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+function EventEmitter() {
+  this.events = {};
+}
+
+EventEmitter.prototype.on = function(eventType, callback) {
+  this.events[eventType] = this.events[eventType] || [];
+  this.events[eventType].push(callback);
+};
+
+EventEmitter.prototype.emit = function(eventType) {
+  if(this.events[eventType].length > 0){
+      this.events[eventType].forEach(function(callback) {
+      callback();
+    });
+    return true;
+  }else{
+    console.log("Listener of type " +eventType+ " has been removed");
+    return false;
+  }
+};
+
+EventEmitter.prototype.removeEventListener = function(eventType, callback = function(){}){
+  var index = this.events[eventType].indexOf(eventType);
+  this.events[eventType].splice(index, 1);
+};
+
+EventEmitter.prototype.removeAllListeners = function(eventType = ""){
+  if (eventType === ""){
+    this.events[eventType] = [];
+  }else{
+    this.events[eventType] = this.events[eventType].filter(function(event_type){
+      event_type !== eventType;
+    });
+  }
+};
+
+
+module.exports = EventEmitter;

fsp.js

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+var fs = require('fs');
+
+var promise_obj = {
+  readFile: function(path, encoding = 'utf-8'){
+    return new Promise(function(resolve, reject){
+      if (path === './data/lorem.txt'){
+        var data = fs.readFileSync(path, encoding);
+        resolve(data);
+      }else{
+        setTimeout(reject('Invalid path'),5000);
+      }
+    });
+  },
+  writeFile: function(path, data, encoding = 'utf-8'){
+    return new Promise(function(resolve, reject){
+      if (path === './data/write_here.txt'){
+          resolve(fs.writeFile(path, data, encoding, function(err){
+            if(err){
+              console.log(err);
+            }else{
+              console.log("Write succeeded!");
+            }
+          }));
+      }else{
+        reject('Write path is invalid');
+      }
+    });
+  },
+
+  appendFile: function(path, data, encoding = 'utf-8'){
+    return new Promise(function(resolve, reject){
+      if (path === './data/write_here.txt'){
+         resolve(fs.appendFile(path, data, encoding = 'utf-8', function(err){
+           (err)?console.log(err):console.log("append was successful!");
+         }));
+      }else{
+        reject('Invalid file to append data');
+      }
+    });
+  }
+};
+
+
+module.exports = promise_obj;

promises.js

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+//Simple Promise that resolves to hello world
+var p = Promise.resolve("Hello Promise!");
+//Resolving the above promise using then
+p.then(function(message){
+  setTimeout(function(){
+    console.log(message)}, 1000);
+  });
+
+// Working code
+// function delay(milliseconds){
+//   return new Promise(function(resolve, reject){
+//     resolve(setTimeout(function(){
+//       console.log(milliseconds)
+//     }, milliseconds));
+//   });
+// }
+
+//Working code
+function delay(ms) {
+      return new Promise(resolve => {
+              setTimeout(() => {
+                 resolve(ms > 0 ? ms : 'Done!');
+               }, ms);
+             });
+}
+
+function countDown(ms) {
+             console.log(ms);
+             return delay(ms - 100);
+}
+
+delay(300)
+    .then(countDown)
+    .then(countDown)
+    .then(countDown)
+    .then(countDown)
+    .then(countDown);
+
+
+//Function that returns a Promise
+function squared(num){
+  return new Promise(
+    function(resolve, reject){
+    if (typeof num === 'number'){
+      var op = num*num;
+      resolve(op);
+    }else{
+      var err = 'Input is not a number!';
+      reject(err);
+    }
+  }
+);
+}
+
+//Promise is resolved
+squared(3)
+.then(function(result){
+  console.log(result);
+},
+function(error){
+  console.log(error);
+});
+
+//Array of promises
+var arr = [1,2,3,4,5,6,7,8,9];
+var arr_promises = arr.map(function(elem){
+   return squared(elem);
+ });
+
+ //Array of promises resolved
+ Promise.all(arr_promises)
+ .then(function(results){
+   console.log(results);
+ });
+
+//Working code - Using catch and then
+function doBadThing(forRealz){
+  return new Promise(function(resolve, reject){
+    if (forRealz === false){
+      resolve('Yay!');
+    }else{
+      reject('error');
+    }
+  });
+}
+
+doBadThing(false)
+.then(function(result){
+  console.log(result);
+},
+function(error){
+  console.error(error);
+});
+
+//*****catch not triggered*****
+doBadThing(true)
+ .then(function(result){
+   console.log(result);
+   throw "Trigger the catch!";
+ })
+ .catch(function(err){
+   console.error(err);
+ });
+
+//Working code
+var fsp = require('./fsp');
+fsp.readFile('./data/lorem.txt')
+.then(function(result){
+  console.log(result);
+})
+.catch(function(err){
+  console.error(err);
+});
+
+fsp.writeFile('./data/write_here.txt', 'hello')
+.then(function(result){
+  console.log(result);
+})
+.catch(function(err){
+  console.log(err);
+});
+
+//throwing error
+fsp.appendFile('./data/write_here.tx', ' File operations succeeded!')
+.then(function(result){
+  console.log(result);
+})
+.catch(function(err){
+  console.log(err);
+  //throw "Append failed!";
+});
+
+//Event Emitter
+ var Emitter = require('./emitter');
+ //debugger;
+ var emitter = new Emitter();
+ //emitter.on('shout');
+
+ emitter.on("click", function(){
+   console.log("hellooo!");
+   //debugger;
+ });
+
+ emitter.on("scream", function(){
+   console.log("Errrrrrr!!!");
+   //debugger;
+ });
+
+
+ emitter.emit("scream");
+
+ emitter.emit("click");
+
+ emitter.removeEventListener("click", function(){
+   console.log("Removed Listener");
+ });
+
+ emitter.emit("click");
+
+ emitter.removeAllListeners();
+
+console.log(emitter.emit("click"));