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In this lecture, we are going to explore one more flattening operator called Exhaust Map Siemens before

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it'll subscribe to inner observables values emitted by the observable are pushed to the stream.

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What sets it apart is that it'll ignore incoming observables.

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If an observable is active, let's say we have an interval observable running in the background intervals

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don't end until we force the observable to complete.

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Therefore, values will continue to be emitted if a new observable is created.

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The exhaust map operator will ignore the observable.

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A subscription will never be made to the observable.

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As long as there is an active subscription, subsequent observables are ignored.

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The first observable will continue to push data.

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It's not a common operator to use, but it can be useful if you want to wait for a current observable

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to complete before moving on.

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For example, if you're developing a form, you may want to prevent duplicate submissions during your

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request.

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You can use the exhaust map operator to avoid multiple requests from occurring while the initial request

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is being processed.

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Let's try playing with the operator in the important statements and the exhaust map operator.

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Next, where you place the icon cap map operator with the exhaust map operator.

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The arguments for this operator can remain unchanged.

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The flattening operators all have similar arguments in the browser.

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Let's turn throttling on.

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Lastly, let's click on the button.

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If we look under the network panel, the request is being performed.

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The Exhaust Map operator successfully subscribes to the observable after the request has been made.

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We can click on the button again to initiate more requests.

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However, if we double click on the button, a second request is never initiated.

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The exhaust map operator has ignored the second request because the first request is ongoing.

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You should be careful with this operator if you don't want your observables to be ignored.

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You may want to look for a different operator.

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This operator can be helpful in preventing users from spamming form submissions.

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That wraps it up for the flattening operators in the next lecture.

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Let's do a quick recap before moving on.