Troubleshooting Observable data in Angular 2/Typescript - A Comprehensive Guide

Question

Troubleshooting Observable data in Angular 2/Typescript - A Comprehensive Guide

After going through the Angular 2 tutorial, I managed to create a search feature that asynchronously displays a list of heroes.

<div *ngFor="let hero of heroes | async">
    {{hero.name}}
</div>

In my component, I have an observable array of heroes:

heroes: Observable<Hero[]>;

However, when I tried implementing a similar feature in my application, nothing appeared on the screen and no errors were reported. To investigate further, I opened the debugger in Chrome and attempted to inspect the "heroes" variable, only to find it wrapped in an Observable object.

Is there a way to view the current or last value in the debugger, or perhaps another technique to debug this type of issue?

angular typescript rxjs observable rxjs5

Answer 1

Answer №1

When working with RxJS version 6 and above, the tap() operator is now used instead of do(). The usage will be as shown below:

someStream$.pipe(
  map(data => data.something),
  tap(something => console.log(something)),
)

Answer 2

When working with RxJS version 6 and above, the tap() operator is now used instead of do(). The usage will be as shown below:

someStream$.pipe(
  map(data => data.something),
  tap(something => console.log(something)),
)

Answer 3

Answer №2

There are numerous articles discussing this topic, but one of the most straightforward methods is to utilize the do() operator to observe what is happening in your operator chains.

For further reading:

https://github.com/Reactive-Extensions/RxJS/blob/master/doc/gettingstarted/testing.md#debugging-your-rx-application
How to debug rxjs5?

Answer 4

There are numerous articles discussing this topic, but one of the most straightforward methods is to utilize the do() operator to observe what is happening in your operator chains.

For further reading:

https://github.com/Reactive-Extensions/RxJS/blob/master/doc/gettingstarted/testing.md#debugging-your-rx-application
How to debug rxjs5?

Answer 5

Answer №3

Before anything else, for those utilizing typescript, keep in mind:

characters: Observable<Array<Character>>;

To display it, just include the following in your script:

characters.subscribe((v) => console.log('received updated characters list: ', v));

Answer 6

Before anything else, for those utilizing typescript, keep in mind:

characters: Observable<Array<Character>>;

To display it, just include the following in your script:

characters.subscribe((v) => console.log('received updated characters list: ', v));

Answer 7

Answer №4

To implement the do() operator, use the following example:

this.http
        .get('someUrl', options)
        .map(res => res.json())
        .do(
            data => {
                console.log(data);
            },
            error => {
                console.log(error)
            }
        )

If nothing occurs within the do() functions, it indicates that you have not subscribed to the observable yet. Remember, observables require a subscription to execute any actions.

Answer 8

To implement the do() operator, use the following example:

this.http
        .get('someUrl', options)
        .map(res => res.json())
        .do(
            data => {
                console.log(data);
            },
            error => {
                console.log(error)
            }
        )

If nothing occurs within the do() functions, it indicates that you have not subscribed to the observable yet. Remember, observables require a subscription to execute any actions.

Answer 9

Answer №5

One way to display log messages in Angular is by using the .pipe() method.

constructor(
    private data: Data<any>
  ) {
    this.property= this.data.select<any>(state => state.property).pipe(
        tap(Item => console.log('Property: ', Item ))
    );
  }

Answer 10

One way to display log messages in Angular is by using the .pipe() method.

constructor(
    private data: Data<any>
  ) {
    this.property= this.data.select<any>(state => state.property).pipe(
        tap(Item => console.log('Property: ', Item ))
    );
  }

Answer 11

Answer №6

If you need a tool for debugging with console.log, check out my custom function logValues() in the library s-rxjs-utils. Just follow the instructions provided in the documentation:

of(3, 4).pipe(logValues()).subscribe();
// output will be logged using console.log:
// [value] 3
// [value] 4
// [complete]

You can even include a message to display alongside the values and set the desired log level.

Answer 12

If you need a tool for debugging with console.log, check out my custom function logValues() in the library s-rxjs-utils. Just follow the instructions provided in the documentation:

of(3, 4).pipe(logValues()).subscribe();
// output will be logged using console.log:
// [value] 3
// [value] 4
// [complete]

You can even include a message to display alongside the values and set the desired log level.

Troubleshooting Observable data in Angular 2/Typescript - A Comprehensive Guide

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

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