如何在 concat 运算符完成后执行代码

Question

I have tasks (observables) in array and want run them sequentially and at the end I want to run some finish code

 const { concat, of, tap } = rxjs; const { delay } = rxjs.operators; let tasks = [ of(1).pipe(delay(1000)), of(2).pipe(delay(2000)), of(3).pipe(delay(1000)), of(4).pipe(delay(2000)), ]; // In below example, word "Finish" is printed 4 times // but I want print it only once, at the end. concat(...tasks).pipe(tap(()=> console.log('Finish'))).subscribe(n => console.log(`result for task ${n}`));

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I try to use tap but without success - how to do it?

Answer 1

Tap, how you use, will run on each emited value.

You should use finalize instead.

 const { concat, of, finalize } = rxjs; const { delay } = rxjs.operators; let tasks = [ of(1).pipe(delay(1000)), of(2).pipe(delay(2000)), of(3).pipe(delay(1000)), of(4).pipe(delay(2000)), ]; concat(...tasks).pipe(finalize(()=> console.log('Finish'))).subscribe(n => console.log(`result for task ${n}`));

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