Anil Singh | Code-sample.com

How to set a custom header on the request? To set a custom header on the request, firstly we need to instantiate HttpHeaders() object and pass ('header',   'value') into a function. let headers = new HttpHeaders (). set ( 'Content-Type' , 'text' ); In the above example we set “Content-Type” header value to be “text” and the default header “Content-Type” is – “application/json” It is of type immutable Map so if you assign a new value it will reinitialize the object. let requestHeaders = new HttpHeaders (). set ( 'Content-Type' , 'application/json' ); requestHeaders = requestHeaders . set ( 'authorization' , 'Bearer ' + token ); We can also append headers by chaining HttpHeaders() constructor and will look like this- let requestheaders = new HttpHeaders (). set ( 'Content-Type' , 'application/json' )                     . set ( 'authorization' , 'Bearer '...

What Are HttpHeaders? The Http Headers is immutable Map and each and every set() returns a new instance and applies the changes with lazy parsing. An immutable set of Http headers, with lazy parsing. HttpHeaders Constructor - constructor ( headers ?: string | { [name: string]: string | string [];}); Imports HttpHeaders from - import { HttpHeaders } from '@angular/common/http' ; HttpHeaders class contains the list of methods - 1.       has() - Checks for existence of header by given name. 2.       get() - Returns the first header that matches given name. 3.       keys() - Returns the names of the headers 4.       getAll() - Returns list of header values for a given name. 5.       append() - Append headers by chaining. 6.       set() -   To set a custom header on the request for a given name ...

What Is HttpClient in Angular? What Is the role and responsibility of HttpClient? HttpClient is performing HTTP requests and responses. Most of all web applications communicate with backend services over the HTTP protocol and all modern browsers support two different APIs for making HTTP requests i.e. 1.       XMLHttpRequest interface 2.       fetch() APIs The HttpClient is more modern and easy to use the alternative of HTTP. HttpClient is an improved replacement for HTTP. They expect to deprecate http in Angular 5 and remove it in a later version.   The new HttpClient service is included in the HTTP Client Module that used to initiate HTTP request and responses in angular apps. The HttpClientModule is a replacement of HttpModule. HttpClient also gives us advanced functionality like the ability to listen for progress events and interceptors to modify requests or responses. Before using the HttpClient...