Promises vs Observables vs Subjects

Let’s explore Promises, Observables, and Subjects in RxJS in greater detail, including examples for each concept.

Promises:

Promises are a fundamental part of JavaScript, providing a way to handle asynchronous operations. A Promise represents a value which might be available now, or in the future, or never.

Characteristics of Promises:

1. Single Value: Promises represent a single value that will be resolved or rejected.
2. Immutable State: Once a Promise is resolved or rejected, its state cannot be changed.
3. Error Handling: Promises have built-in error handling through .catch() or try...catch blocks.

Example:

Consider an asynchronous operation like fetching data from an API.

function fetchData() {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve('Data fetched successfully!');
        }, 2000);
    });
}

fetchData()
    .then(data => {
        console.log(data); // Output: Data fetched successfully!
    })
    .catch(error => {
        console.error(error);
    });

In this example, fetchData() returns a Promise that resolves after 2 seconds, simulating an asynchronous operation.