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

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.