Promises help to function with asynchronous operations. They work in two conditions. They either return a single value when the promise resolves or an error message when the promise gets rejected. Whenever a request is made from a promise, it becomes a non-cancellable command.

On the other hand, observable can be regarded as a stream. It can be anything, a stream of data or events. It can be canceled, unlike promise. An observable can be easily converted into a promise by specifying a command “toPromise( )” with the command to do so.

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BY Best Interview Question ON 24 Feb 2020