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How to fix Angular HttpClient toPromise() deprecated (rxjs)

Problem:

You have angular HTTP client code like

httpclient_toPromise.ts
this.http.get<MyType>(`${this.baseURL}/api/myAPI`).toPromise()

but toPromise() is deprecated in recent versions of angular / rxjs.

toPromise_deprecation.ts
/** @deprecated Replaced with {@link firstValueFrom} and {@link lastValueFrom}. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise */
toPromise(): Promise<T | undefined>;

Solution

In most cases, for HttpClient, you want to use rxjs’s firstValueFrom() since the HttpClient Observables typically only return one value anyway.

First, import firstValueFrom from rxjs:

import_firstValueFrom.ts
import { firstValueFrom } from 'rxjs';

then remove the .toPromise() call:

remove_toPromise.ts
// Before
this.http.get<MyType>(`${this.baseURL}/api/myAPI`).toPromise()
// After
this.http.get<MyType>(`${this.baseURL}/api/myAPI`)

and surround the entire statement with firstValueFrom:

use_firstValueFrom.ts
// Before
this.http.get<MyType>(`${this.baseURL}/api/myAPI`)
// After
firstValueFrom(this.http.get<MyType>(`${this.baseURL}/api/myAPI`).toPromise())

This will fix the issue.

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