Debugging NodeJS Applications

יום שלישי, אוקטובר 6, 2015

With the introduction of Microsoft Visual Studio Code, debugging of NodeJS application is now a quite simple procedure to follow For example, suppose we have the following NodeJS super simple application console.log("Hello NodeJS"); and we would like to debug it (although there is no much to debug) Just open command line prompt. Switch to the directory containing your JavaScript file and type code . I am assuming that you already installed Visual Studio Code from here (very short installation). Now, Visual Studio Code should open and display the list of files under the current directory Double click the app.js file, set a breakpoint using F9 and press F5 The debug...
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Bringing the simplicity of Attributes/Annotations into Angular 1.X

יום שני, ספטמבר 28, 2015

One of the more interesting features of Angular 2 is its improved dependency injection mechanism Unlike Angular 1.X you don't need to specify the dependencies manually in order to preserve minification capabilities Angular 2 is smart enough to use the type information of the dependency and inject the correct implementation at run time Can we do the same with Angular 1.X ? Sure, keep reading ... First lets describe the way we define a controller import {MyApp} from '../App'; import {Controller} from '../Common/Decorators'; import {Contact, ContactService} from '../Services/ContactService'; @Controller(MyApp, "HomeCtrl") class HomeCtrl {     contacts: Contact;     constructor(contactService: ContactService) {         contactService.getAll().then(contacts => {             this.contacts = contacts;         });     } } And the service dependency import {MyApp} from '../App'; import {Service, Inject} from '../Common/Decorators'; @Service(MyApp, "contactService") export class ContactService {     constructor(@Inject("$http") private $http: ng.IHttpService) {     }     getAll(): ng.IPromise<Contact> {         return this.$http.get("/contacts.json").then(response =>;     } } export interface Contact {     id: number;     name: string; } Second we need to define the Controller and Service decorators (A.K.A attribute/annotation) export function Controller(module: ng.IModule, name: string) {     return function (target: Function) {         Reflect.defineMetadata("controller", target, { controllerName: name });         module.controller(name, target);         set$inject(target);     } } export function Service(module: ng.IModule, name: string) {     return function (target: Function) {         Reflect.defineMetadata("service", { serviceName: name }, target);         module.service(name, target);         set$inject(target);     } } For more information on...

Typescript 1.6 – Async & Await

יום שני, ספטמבר 21, 2015

The Promise pattern simplifies JavaScript asynchronous function management While using promises is much cleaner than using naive callbacks the code still does not look so nice and tidy Consider the following, function getValue() { return asyncStep1().then(function () { return asyncStep2().then(function () { return asyncStep3(); }); }); } The sample code invokes three asynchronous functions one after the other and returns the output of the last function (step3) Using Typescript 1.6 you can just write the following async function getValue() {     await asyncStep1();     await asyncStep2();     return await asyncStep3(); } Much better, right ? The async feature is considered experimental which means that it is turned off by default. If you are using Typescript from the command line (using NodeJS) then you need to add the --experimentalAsyncFunctions option In case you are compiling Typescript within VisualStudio 2015 then...
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Managing long running operation using promise and $$q

יום ראשון, אפריל 5, 2015

Through my previous post I described the challenges when implementing long running operation. Basically, you need to break your long running operation into small steps where each step is isolated by setTimeout(0) from the next step. At this post I would like to cover a technique for using promise object to manage the long running operation. Angular's promises offer the common then/catch functions but also offer an additional function named notify The notify function can be used to send notifications to the client about the progress of the running operation. For example, suppose a runTask function is responsible for initiating a long running...
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Updating DOM during long running operation

יום שבת, מרץ 21, 2015

Suppose I need to implement a long running operation (longer than a few seconds) and during that operation display some user feedback Well, JavaScript is single threaded. This means that during operation execution the single thread is busy and cannot handle UI events like mouse move and mouse click. From end user perspective the UI is dead. Modern solution is to use Web Worker. As long as your algorithm is pure (only accesses JavaScript objects) then you are OK. However, if the algorithm needs to access DOM objects you cannot use web workers since they have no access to the DOM I agree that...