Promises vs Observables - Angular Tutorial

Published: 10 June 2024
on channel: Quick Code Academy

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In this video I have explained the key differences between promise and observables.
Promises and Observables are both tools used for handling asynchronous operations in JavaScript, but they have some key differences:

Promise -
Single Value: A Promise represents a single value that may be available now, in the future, or never. Once it is resolved or rejected, it cannot be changed.
Eager Execution: Promises start executing immediately when created.
Not Lazy: Promises are not lazy; they do not wait for subscription or call to start.
Not Cancelable: Once a Promise starts, it cannot be canceled.
Simple Error Handling: Promises have straightforward error handling using .then() for success and .catch() for errors.
Chaining: Promises support chaining to handle a sequence of asynchronous operations.

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Observable-
Multiple Values: An Observable can emit multiple values over time, which makes it suitable for scenarios like events or streams of data.
Lazy Execution: Observables are lazy; they don’t start emitting values until a subscription is made.
Cancelable: Observables can be canceled by unsubscribing, which stops the emission of values.
Complex Error Handling: Observables provide more complex error handling mechanisms and can retry or handle errors in sophisticated ways.
Operators: Observables come with a variety of operators (map, filter, reduce, etc.) that allow for powerful manipulation of the emitted values.
Streams: Observables are often used to handle streams of data, making them suitable for real-time applications.
In summary, Promises are great for handling a single asynchronous value, while Observables are more powerful for dealing with multiple values or streams of asynchronous data.

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