Clara  Gutmann

Clara Gutmann


How to Cache HTTP Requests In Angular

Table of Content

Angular is a great choice for any large scale enterprise projects because it is opinionated and brings the whole team together on many things. It is like having a headstart for your development team. Though angular has so many things defined, still there are some things that you have to figure out on your own.

One such thing is caching HTTP requests, as per the famous quote by Phil Karlton,

“There are only two hard things in Computer Science: cache invalidation and naming things.”, Caching things is very easy but clearing the cache is difficult. We are going to see an approach that puts you in control of both caching an HTTP request and invalidating the cache.

First, let’s define a property in your service which caches the result of the HTTP request

data-sheets-value=“{“1”:2,“2”:“private userList$: Observable;”}” data-sheets-userformat=“{“2”:513,“3”:{“1”:0},“12”:0}”>private userList$: Observable;

I’m using any type here for the sake of example, in real-world applications you should not be using any type like this. Now let us write the service method that makes the HTTP request.

public getUsers$(): Observable {

if (!this.userList$) {

this.userList$ = this.httpClient.get(‘/users’);


return this.userList$;


The above code is pretty self-explanatory, we are checking if the observable is already defined and if it isn’t we are making the HTTP call and then store the reference in the member observable we created. Next time this function gets called, the existing reference to the observable will be returned without actually making a fresh HTTP call.

#angular #http #development #coding

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How to Cache HTTP Requests In Angular
Christa  Stehr

Christa Stehr


Install Angular - Angular Environment Setup Process

Angular is a TypeScript based framework that works in synchronization with HTML, CSS, and JavaScript. To work with angular, domain knowledge of these 3 is required.

  1. Installing Node.js and npm
  2. Installing Angular CLI
  3. Creating workspace
  4. Deploying your First App

In this article, you will get to know about the Angular Environment setup process. After reading this article, you will be able to install, setup, create, and launch your own application in Angular. So let’s start!!!

Angular environment setup

Install Angular in Easy Steps

For Installing Angular on your Machine, there are 2 prerequisites:

  • Node.js
  • npm Package Manager

First you need to have Node.js installed as Angular require current, active LTS or maintenance LTS version of Node.js

Download and Install Node.js version suitable for your machine’s operating system.

Npm Package Manager

Angular, Angular CLI and Angular applications are dependent on npm packages. By installing Node.js, you have automatically installed the npm Package manager which will be the base for installing angular in your system. To check the presence of npm client and Angular version check of npm client, run this command:

  1. npm -v

Installing Angular CLI

  • Open Terminal/Command Prompt
  • To install Angular CLI, run the below command:
  1. npm install -g @angular/cli

installing angular CLI

· After executing the command, Angular CLI will get installed within some time. You can check it using the following command

  1. ng --version

Workspace Creation

Now as your Angular CLI is installed, you need to create a workspace to work upon your application. Methods for it are:

  • Using CLI
  • Using Visual Studio Code
1. Using CLI

To create a workspace:

  • Navigate to the desired directory where you want to create your workspace using cd command in the Terminal/Command prompt
  • Then in the directory write this command on your terminal and provide the name of the app which you want to create. In my case I have mentioned DataFlair:
  1. Ng new YourAppName

create angular workspace

  • After running this command, it will prompt you to select from various options about the CSS and other functionalities.

angular CSS options

  • To leave everything to default, simply press the Enter or the Return key.

angular setup

#angular tutorials #angular cli install #angular environment setup #angular version check #download angular #install angular #install angular cli

Angular Server Side Rendering State Transfer For HTTP Requests

This tutorial extends the SSR explained on Server-side rendering (SSR) with Angular Universal page. This tutorial fixes the content flash occurs on SSR write after page loads due to content refresh caused by data received through network requests. If you are crazy about PageSpeed/Web Vitals score as much as me, this will help you to improve:

  1. Largest Contentful Paint (LCP)
  2. First Input Delay (FID)
  3. Cumulative Layout Shift (CLS)

I have tested this on Angular 9 and 10.

Before continuing, please make sure you have SSR set up as mentioned on Our goal is to store data received from SSR and reuse them without making any network requests.

  1. Create a HttpInterceptor to intercept SSR HTP requests and store results on TransferState service
  2. Add interceptor to the app.server.module.ts*
  3. Create a HttpInterceptor to intercept HTP requests happen on the client-side and return result from state service instead of making a network request
  4. Add interceptor to the app.module.ts*

*app.module is the module where you put modules required to render things on the browser. app.server.module is where you put things required for the rendering page on the server.

Step 1: Interceptor for SSR to cache HTTP requests

import { HttpHandler, HttpInterceptor, HttpRequest, HttpResponse } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { makeStateKey, TransferState } from '@angular/platform-browser';
import { tap } from 'rxjs/operators';

export class ServerStateInterceptor implements HttpInterceptor {

    constructor(private transferState: TransferState) { }

    intercept(req: HttpRequest<any>, next: HttpHandler) {
        return next.handle(req).pipe(
            tap(event => {
                if ((event instanceof HttpResponse && (event.status === 200 || event.status === 202))) {
                    this.transferState.set(makeStateKey(req.url), event.body);

Here the transferState is the service that has the data store. This data store is serialized and passed to the client-side with the rendered page.

intercept()is the method we have to implement from HttpInterceptor interface.

Angular renderer waits for your asynchronous task to be executed before generating the HTML page. After we add this interceptor to the server module, all the HTTP requests you do will go through this interceptor. On the above example, I save all the successful HttpResponses on to the state store.

#angular #server-side-rendering #web-development #seo-optimization #pagespeed #caching #angular-development #angular-application

Hertha  Mayer

Hertha Mayer


Super easy trick to bypass Http Interceptors in Angular

Searching for a better folder structure for angular projects? Check this article out, you can thank me later.

Image for post

Photo by Amir samoh on unsplash

Recently, I have been working on a task, regarding AWS S3 bucket file uploading using Angular and preSigned URLs. In that project, I have used HTTP interceptor to handle my request to bind all header parameters. My problem arose while I was trying upload files and found that I wasn’t able to since there were “two Authorization headers” in that request. They were the usual request header with token and the header which auto binds by the presigned Url. To solve this issue, I found a super-easy solution that allowed me to bypass my HTTP interceptor and BOOM! Issue fixed. Let’s dive into what I did.

Wait… What is an Interceptor?

Before starting the explanation of my trick, let’s get to know what interceptors are and how we can use them.

Angular is one of the most popular front-end development frameworks in the developer community. One of the main reasons for that is that Angular provides many built-in tools that help to scale industry level JavaScript applications. Interceptors are one of the tools in the list capable of handling HTTP requests globally. They allow us to intercept incoming and outgoing HTTP requests using the HttpClient. By intercepting the request we can modify or change any parameter of the request.

Before diving any deeper I suggest that you have a basic knowledge of Angular HTTP Client and RxJS Observable.

Here is the trick

As I mentioned above, there are occasions where we need to allow for a custom header (or, in other words, to skip the interceptor action in http requests).

BONUS POINT:_ Usually in Angular best practices, it is better to keep our services separate from modules, components and models etc. Please checkout the below folder structure. It is better if you can refer to this structure for your future implementations._

 ┣ app
 ┃ ┣ common
 ┃ ┣ customer
 ┃ ┣ models
 ┃ ┣ public
 ┃ ┣ services
 ┃ ┃ ┣ authentication
 ┃ ┃ ┃ ┣ guards
 ┃ ┃ ┃ ┃ ┣ auth.guard.ts
 ┃ ┃ ┃ ┣ interceptors
 ┃ ┃ ┃ ┃ ┣ response.interceptor.ts
 ┃ ┃ ┃ ┗ auth.service.ts
 ┃ ┃ ┣ directives
 ┃ ┃ ┣ pipes
 ┃ ┃ ┣ resolvers
 ┃ ┃ ┣ services-api
 ┃ ┃ ┣ services-inter
 ┃ ┣ app.component.css
 ┃ ┣ app.component.html
 ┃ ┣ app.component.spec.ts
 ┃ ┣ app.component.ts
 ┃ ┣ app.module.ts
 ┃ ┣ app.routing.ts
 ┃ ┗ app.server.module.ts
 ┣ assets
 ┣ environments
 ┣ favicon.ico
 ┣ index.html

As per the file tree, I kept my interceptors inside the _src/services/interceptors _folder.

Image for post

#http-interceptors #angular #http-client #programming #http-request

Roberta  Ward

Roberta Ward


Basics of Angular: Part-1

What is Angular? What it does? How we implement it in a project? So, here are some basics of angular to let you learn more about angular.

Angular is a Typescript-based open-source front-end web application platform. The Angular Team at Google and a community of individuals and corporations lead it. Angular lets you extend HTML’s syntax to express your apps’ components clearly. The angular resolves challenges while developing a single page and cross-platform applications. So, here the meaning of the single-page applications in angular is that the index.html file serves the app. And, the index.html file links other files to it.

We build angular applications with basic concepts which are NgModules. It provides a compilation context for components. At the beginning of an angular project, the command-line interface provides a built-in component which is the root component. But, NgModule can add a number of additional components. These can be created through a template or loaded from a router. This is what a compilation context about.

What is a Component in Angular?

Components are key features in Angular. It controls a patch of the screen called a view. A couple of components that we create on our own helps to build a whole application. In the end, the root component or the app component holds our entire application. The component has its business logic that it does to support the view inside the class. The class interacts with the view through an API of properties and methods. All the components added by us in the application are not linked to the index.html. But, they link to the app.component.html through the selectors. A component can be a component and not only a typescript class by adding a decorator @Component. Then, for further access, a class can import it. The decorator contains some metadata like selector, template, and style. Here’s an example of how a component decorator looks like:

    selector: 'app-root',
    templateUrl: 'app.component.html',
    styleUrls: ['app.component.scss']

Role of App Module

Modules are the package of functionalities of our app. It gives Angular the information about which features does my app has and what feature it uses. It is an empty Typescript class, but we transform it by adding a decorator @NgModule. So, we have four properties that we set up on the object pass to @NgModule. The four properties are declarations, imports, providers, and bootstrap. All the built-in new components add up to the declarations array in @NgModule.

declarations: [
imports: [
bootstrap: [AppComponent]

What is Data Binding?

Data Binding is the communication between the Typescript code of the component and the template. So, we have different kinds of data binding given below:

  • When there is a requirement to output data from our Typescript code in the HTML template. String interpolation handles this purpose like {{data}} in HTML file. Property Binding is also used for this purpose like [property] = “data”.
  • When we want to trigger any event like clicking a button. Event Binding works while we react to user events like (event) = “expression”.
  • When we can react to user events and output something at the same time. Two-way Binding is used like [(ngModel)] = “data”.

image for understanding data binding

#angular #javascript #tech blogs #user interface (ui) #angular #angular fundamentals #angular tutorial #basics of angular

Clara  Gutmann

Clara Gutmann


Angular HttpClient Module | Angular Http GET, POST Example

Angular 9 HttpClient is an inbuilt module that helps us to send network requests to any server. Angular HttpClientModule is used to send GET, POST, PUT, PATCH, and DELETE requests. Angular can consume REST API using the Angular HttpClient module. The latest version of the Angular framework is  Angular 9.

If you are new to Angular 9, then check out my  Angular 9 Tutorial in this blog. Most front-end applications communicate with the backend services over an HTTP protocol. Modern browsers support the two different APIs for making HTTP requests.

  1. XMLHttpRequest interface and the
  2. fetch() API.

We will use XMLHttpRequest for Angular application.

#angular #angular httpclient #angular http #post #get