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7 HttpHeaders

How to set a custom header on the request?

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 ' + token);

And final request with custom headers will look like this –
import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';

export class CustomerService {
  //Inject HttpClient into your components or services
  constructor(private http: HttpClient) { }

  //Set Headers
  requestHeaders = new HttpHeaders().set('Content-Type', 'text')
              .append('Authorization', 'CustomToke_AFA96A3429A9524');
  //Get Customer list
  getCustomers() {
    this.http.get('', {
        headers: this.requestHeaders
    }).map((data:HttpEvent<object>) => { console.log(data) })

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