Completed assignment Async_NodeJS

.gitignore

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+node_modules/

README.md

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 # assignment_async_nodejs
 Async Node.js sprint
+
+<h3>Maddie Rajavasireddy</h3>
+
+Run code using command `node index.js`
+
+Index.js contains solutions for the Warmups and test code for the File Operations and Event Emitter

data/lorem.txt

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+Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
+tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
+quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
+consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
+cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
+proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

data/test.txt

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+Hello!Hello again!

emitter.js

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+'use strict';
+
+const Emitter = function() {
+
+  // store for events and their listeners
+  this.events = {};
+
+
+  // attach a listener for a particular event
+  this.on = function(eventType, callback) {
+
+    // add an event if not there
+    if (this.events[eventType] === undefined) {
+      this.events[eventType] = [];
+    }
+
+    // then attach listeners
+    this.events[eventType].push(callback);
+
+  };
+
+  // invoke all listeners for a particular event 
+  this.emit = function(eventType) {
+
+    let callbacks = this.events[eventType];
+
+    // check if any listeners for this event
+    if (callbacks !== undefined) {
+
+      // loop though all listeners for this event
+      callbacks.forEach(function(callback) {
+        callback();
+      });
+    }  else {
+
+      // output error message if no listeners exist for given event
+      console.log("this event type does not exist");
+    }
+
+  };
+
+  // remove a particular listener of given events
+  this.removeListener = function(eventType, callback) {
+
+    // check if any listeners for this event
+    let callbacks = this.events[eventType];
+
+    if (callbacks !== undefined) {
+
+      //get index of listener to remove	
+      let callbackIndex = callbacks.indexOf(callback);
+
+      if (callbackIndex >= 0) {
+
+        // remove that listener
+        callbacks.splice(callbackIndex, 1);
+      }
+
+    }
+
+  };
+
+  // remove all listeners from a particular event 
+  this.removeAllListeners = function(eventType) {
+
+    //delete all listeners on given event in one go
+    delete this.events[eventType];
+
+  };
+
+}
+
+
+module.exports = Emitter;

fsp.js

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+'use strict';
+
+const fs = require("fs");
+let path = "./data/lorem.txt";
+
+let fsp = {
+  readFile: function(path) {
+    return new Promise((resolve, reject) => {
+      fs.readFile(path, 'utf8', (error, data) => {
+        if(error) {
+          reject(error);
+        }
+        resolve(data);
+      });
+    });
+  },
+
+  writeFile: function(file, data) {
+    return new Promise((resolve, reject) => {
+      fs.writeFile(file, data, (error) => {
+        if(error) {
+          reject(error);
+        }
+        resolve(data);
+      });
+    });
+  },
+
+  appendFile: function(file, data) {
+    return new Promise((resolve, reject) => {
+      fs.appendFile(file, data, (error) => {
+        if(error) {
+          reject(error);
+        }
+        resolve(data);
+      });
+    });
+  },
+};
+
+module.exports = fsp;

index.js

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+'use strict';
+
+const fsp = require("./fsp");
+const Emitter = require("./emitter"); //"events"); -- works just the same after switch out
+
+
+// 1. Create a promise that resolves the message "Hello Promise!" after 1 sec
+let p = Promise.resolve("Hello Promise!");
+
+p.then(function(message) {
+
+  setTimeout(function () {
+    console.log(message);
+  }, 1000);
+
+});
+
+
+// 2. Create a function with the following signature: delay(milliseconds)
+function delay (time) {
+  return new Promise(resolve => setTimeout(resolve(time), time));
+}
+
+function countDown(num) {
+
+  if(num > 0) {
+    console.log(num);
+    num -= 100;
+  } else {
+    console.log('Done!');
+  }
+
+  return num;
+}
+
+delay(1000)
+  .then(countDown) //=> 1000
+  .then(countDown) //=> 900
+  .then(countDown) //=> 800
+  .then(countDown) //=> 700
+  .then(countDown) //=> 600
+  .then(countDown) //=> 500
+  .then(countDown) //=> 400
+  .then(countDown) //=> 300
+  .then(countDown) //=> 200
+  .then(countDown) //=> 100
+  .then(countDown); //=> Done!
+
+
+
+// 3. Create a function that accepts a number and returns a promise
+// that resolves that number squared
+function square(integer) {
+  return new Promise( function(resolve, reject) {
+
+    if(Number.isInteger(integer)) {
+	  resolve(integer * integer);
+	} else {
+	  reject();
+	}
+
+  });
+}  
+
+let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+nums = nums.map(i => square(i));
+
+Promise.all(nums)
+  .then(results => console.log(results));
+
+
+
+// 4. Create a function with this signature doBadThing(forRealz)	
+function doBadThing(forRealz) {
+  return new Promise( function(resolve, reject){
+	if (forRealz == false) {
+	  resolve("Yay!");
+	} else {
+	  reject("Nay!");
+	}
+  });
+}
+
+doBadThing(true).then(function(result) {
+  console.log(result);						
+}, function(err) {										//reject handler
+     console.error("reject message: " + err);
+   }
+);
+
+doBadThing(false)
+  .then(function(result) {
+    console.log(result);
+    throw "Trigger the catch!";							//throw error
+  })
+  .catch(function(err) {								//catch error
+    console.error("catch message: " + err);
+  });   
+
+
+
+// File Operations using Promises
+// readFile, writeFile, appendFile
+
+fsp.readFile("./data/lorem.txt")
+  .then(function(data) {
+    // Outputs the file data
+    console.log(data);
+  })
+  .catch(function(err) {
+    console.error(err);
+  }
+);
+
+fsp.writeFile("./data/test.txt", "Hello!")
+  .then(function(res) {
+    // Outputs the file data
+    // after writing
+    console.log(res);
+  })
+  .catch(function(err) {
+    console.error(err);
+  }
+);
+
+fsp.appendFile("./data/test.txt", 'Hello again!')
+  .then(function(res) {
+    // Outputs the file data
+    // after appending
+    console.log(res);
+  })
+  .catch(function(err) {
+    console.error(err);
+  }
+);
+
+
+
+// Event Emitter
+// Create an event emitter similar to the NodeJS EventEmitter but a smaller version
+//  Should be able to: 
+// 	a. attach an event listener with `.on(eventType, callback)`
+// 	b. invoke all listeners attached to a particular event with `.emit(eventType)`
+//	c. remove a particular listener from the given event with `.removeListener(eventType, callback)`
+//	d. remove all listeners from the given event with `.removeAllListeners(eventType)`
+
+// Set up Emitter
+let emitter = new Emitter();
+
+const callback1 = function(){
+  console.log("Click 1");
+};
+
+// Attach an event listener on click event
+emitter.on("click", callback1);
+
+// Attach another listener on click event
+emitter.on("click", function(){
+  console.log("Click 2");
+});
+
+// Attach another listener on click event
+emitter.on("click", function(){
+  console.log("Click 3");
+});
+
+// Attach a listener on change event
+emitter.on("change", function(){
+  console.log("Change 1");
+});
+
+// Attach another listener on change event
+emitter.on("change", function(){
+  console.log("Change 2");
+});
+
+
+// Emit a click event - should result in all listeners attached to click event being invoked
+console.log("Print out all listeners on click event");
+emitter.emit("click");
+
+// Emit a change event - should result in all listeners attached to change event being invoked
+console.log("Print out all listeners on change event");
+emitter.emit("change");
+
+console.log("Remove Click 1 listener on click event");
+emitter.removeListener("click", callback1);
+
+// Emit a click event - should result in all listeners attached to click event being invoked
+console.log("Print out all listeners on click event - should have Click 2 and Click 3");
+emitter.emit("click");
+
+// Remove all listeners on an event with emitter.removeAllListeners(eventType)
+console.log("Remove all listeners on click event");
+emitter.removeAllListeners("click");
+
+// Emit a click event - should result in all listeners attached to click event being invoked
+console.log("Print out all listeners on  click event - should not have any left");
+emitter.emit("click");
+
+
+

package.json

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+{
+  "name": "assignment_async_nodejs",
+  "version": "1.0.0",
+  "description": "Async Node.js sprint",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/maddiereddy/assignment_async_nodejs.git"
+  },
+  "author": "Maddie Rajavasireddy",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/maddiereddy/assignment_async_nodejs/issues"
+  },
+  "homepage": "https://github.com/maddiereddy/assignment_async_nodejs#readme"
+}