Angular 4.3 - HttpClient set params

Question

let httpParams = new HttpParams().set('aaa', '111'); httpParams.set('bbb', '222'); 

Why this doesn't work? It only set the 'aaa' and NOT the 'bbb'

Also, I have an object { aaa: 111, bbb: 222 } How can I set all the values without looping?

UPDATE (this seems to work, but how can avoid the loop?)

let httpParams = new HttpParams(); Object.keys(data).forEach(function (key) {      httpParams = httpParams.append(key, data[key]); }); 

Answer 1

Before 5.0.0-beta.6

let httpParams = new HttpParams(); Object.keys(data).forEach(function (key) {      httpParams = httpParams.append(key, data[key]); }); 

Since 5.0.0-beta.6

Since 5.0.0-beta.6 (2017-09-03) they added new feature (accept object map for HttpClient headers & params)

Going forward the object can be passed directly instead of HttpParams.

getCountries(data: any) {     // We don't need any more these lines     // let httpParams = new HttpParams();     // Object.keys(data).forEach(function (key) {     //     httpParams = httpParams.append(key, data[key]);     // });      return this.httpClient.get("/api/countries", {params: data}) } 

Answer 2

HttpParams is intended to be immutable. The set and append methods don't modify the existing instance. Instead they return new instances, with the changes applied.

let params = new HttpParams().set('aaa', 'A');    // now it has aaa params = params.set('bbb', 'B');                  // now it has both 

This approach works well with method chaining:

const params = new HttpParams()   .set('one', '1')   .set('two', '2'); 

...though that might be awkward if you need to wrap any of them in conditions.

Your loop works because you're grabbing a reference to the returned new instance. The code you posted that doesn't work, doesn't. It just calls set() but doesn't grab the result.

let httpParams = new HttpParams().set('aaa', '111'); // now it has aaa httpParams.set('bbb', '222');                        // result has both but is discarded