Interview Questions
1. What is the difference between Observables and Promises in Angular?
In Angular, as soon as we make a promise, the execution takes place, but this is not the case with observables because they are lazy. It means nothing happens until a subscription is made.
| Promise | Observable |
|---|---|
| It emits a single value. | It emits multiple values over a period of time. |
| Not Lazy | Lazy. An observable is not called until we subscribe to the observable. |
| We can not cancel it. | We can cancel it by using the unsubscribe() method. |
| Observable provides operators like map, forEach, filter, reduce, retry, retryWhen, etc. |
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