Strategies for managing the outcome of the most recent asynchronous request in Angular?

Question

Strategies for managing the outcome of the most recent asynchronous request in Angular?

Encountered a bug related to debounced input and response handling.

A search input triggers server queries as you type with a debounce set to 300ms. However, there are instances of unexpected behavior:

If a user types "ab", waits 300ms, then types "c" before the initial request is resolved, they will see "abc" in the search bar but two network requests are made. Sometimes, the second request for "abc" resolves first, only to be overwritten by the results from the first request for "ab". This leads to displaying results for "ab" while the search input shows "abc".

This seems more like an issue of handling promises rather than just debounce functionality. There should be a way to discard older promises once new ones are made so they don't interfere with accurate responses.

Basically, what's desired:

User types "ab"
Sends request "ab"
User types "c"
Sends request "abc"
Receives response for "abc", handles promise resolution
Receives response for "ab", ignores promise

Are there any established patterns or approaches within Angular to tackle this issue? It seems like it would be a common challenge.

For example, something along the lines of "Resolving only the most recent created promise"?

javascript angularjs promise debouncing

Answer 1

Answer №1

If you're looking for a solution that involves RxJS, Angular 2 natively supports it. However, even in Angular 1, you can incorporate this library by checking out the official rx.angular.js library on this link.

By including this library, you'll be able to tackle your problem with the following code:

HTML

<input type="text" ng-model="search">

JavaScript

observeOnScope($scope, 'search')
  .debounceTime(300)
  .distinctUntillChanged()
  .switchMap(search)
  .safeApply($scope, function (data) {
     $scope.data = data;
  })
  .subscribe();

function search() {
  return rx.Observable.fromPromise($http({ ... }));
}

For more detailed information, check out an extended article at this source

Answer 2

If you're looking for a solution that involves RxJS, Angular 2 natively supports it. However, even in Angular 1, you can incorporate this library by checking out the official rx.angular.js library on this link.

By including this library, you'll be able to tackle your problem with the following code:

HTML

<input type="text" ng-model="search">

JavaScript

observeOnScope($scope, 'search')
  .debounceTime(300)
  .distinctUntillChanged()
  .switchMap(search)
  .safeApply($scope, function (data) {
     $scope.data = data;
  })
  .subscribe();

function search() {
  return rx.Observable.fromPromise($http({ ... }));
}

For more detailed information, check out an extended article at this source

Answer 3

Answer №2

To simplify this process, you can utilize subscriptions in your code.

import { Subscription } from 'rxjs';  

export class DisplayComponent {
    constructor() {}
    
    subscription: Subscription;

    fetchData() {
        // Check if there is an existing subscription and unsubscribe
        if (this.subscription) {
            this.subscription.unsubscribe();
        }

        this.subscription = this._http.getData(url).subscribe(
          data => {
            console.log(data);
          },
          error => {
            console.log(error);
          }
        )
      }
}

Answer 4

To simplify this process, you can utilize subscriptions in your code.

import { Subscription } from 'rxjs';  

export class DisplayComponent {
    constructor() {}
    
    subscription: Subscription;

    fetchData() {
        // Check if there is an existing subscription and unsubscribe
        if (this.subscription) {
            this.subscription.unsubscribe();
        }

        this.subscription = this._http.getData(url).subscribe(
          data => {
            console.log(data);
          },
          error => {
            console.log(error);
          }
        )
      }
}

Strategies for managing the outcome of the most recent asynchronous request in Angular?

Answer №1

Answer №2

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