angular2+ HttpParams Example

getTest() {
  const paramsSet = new HttpParams().set('fromDate', '2018-06-01');
  const paramsFromString = new HttpParams({fromString : 'fromDate=2018-01-01'});
  const paramsFromObject = new HttpParams({fromObject : {fromDate : '2018-02-01'
  }});
  this.http.get('http://localhost:3000/testData', {params: paramsFromObject}).subscribe(data => {
    console.log(data);
  });
}

const params = new HttpParams();

params.set('fromDate' , '2018-06-01');

은 동작하지 않는다.