How to pass url arguments (query string) to a HTTP request on Angular?

I would like to trigger HTTP request from an Angular component, but I do not know how to add URL arguments (query string) to it.

this.http.get(StaticSettings.BASE_URL).subscribe(
  (response) => this.onGetForecastResult(response.json()),
  (error) => this.onGetForecastError(error.json()),
  () => this.onGetForecastComplete()
)

Now my StaticSettings.BASE_URL is like a URL without query string like: http://atsomeplace.com/ but I want it to be like http://atsomeplace.com/?var1=val1&var2=val2

How to add var1, and var2 to my HTTP request object as an object?

{
  query: {
    var1: val1,
    var2: val2
  }
}

and then just the HTTP module does the job to parse it into URL query string.

Solution

The HttpClient methods allow you to set the params in it's options.

You can configure it by importing the HttpClientModule from the @angular/common/http package.

import {HttpClientModule} from '@angular/common/http';

@NgModule({
  imports: [ BrowserModule, HttpClientModule ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}

After that you can inject the HttpClient and use it to do the request.

import {HttpClient} from '@angular/common/http'

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Hello {{name}}</h2>
    </div>
  `,
})
export class App {
  name:string;
  constructor(private httpClient: HttpClient) {
    this.httpClient.get('/url', {
      params: {
        appid: 'id1234',
        cnt: '5'
      },
      observe: 'response'
    })
    .toPromise()
    .then(response => {
      console.log(response);
    })
    .catch(console.log);
  }
}

For angular versions prior to version 4 you can do the same using the Http service.

The Http.get method takes an object that implements RequestOptionsArgs as a second parameter.

The search field of that object can be used to set a string or a URLSearchParams object.

An example:

 // Parameters obj-
 let params: URLSearchParams = new URLSearchParams();
 params.set('appid', StaticSettings.API_KEY);
 params.set('cnt', days.toString());

 //Http request-
 return this.http.get(StaticSettings.BASE_URL, {
   search: params
 }).subscribe(
   (response) => this.onGetForecastResult(response.json()), 
   (error) => this.onGetForecastError(error.json()), 
   () => this.onGetForecastComplete()
 );

The documentation for the Http class has more details. It can be found here and an working example here.