How to use JavaScript Promises in the industry :-
Ecommerce:
Promises are a way to handle asynchronous operations more cleanly and manage errors effectively.
- E-commerce platforms often rely on external APIs for various functionalities like product catalog, payment processing, or shipping calculations. When making API requests, use the fetch API or a library like Axios that returns promises.
fetch('https://api.example.com/products')
.then(response => response.json())
.then(data => {
// Handle the API response data
})
.catch(error => {
// Handle errors
});
Promises are a fundamental concept in asynchronous programming in JavaScript.
They provide a way to handle asynchronous operations more cleanly and manage the flow of asynchronous code.
****The core concepts of promises include:
-
States:
- Promises have three possible states:
- Pending: The initial state when a promise is created, representing that the operation is ongoing or hasn't completed yet.
- Fulfilled: The state when the asynchronous operation is successfully completed, and a result value is available.
- Rejected: The state when the asynchronous operation encounters an error or fails, and an error reason is provided.
- Promises have three possible states:
-
Callbacks:
- Promises use two callback functions to handle their states:
-
resolve(): A function called when the promise is successfully fulfilled. It passes a result value to any attached
.then()
handlers. -
reject(): A function called when the promise is rejected due to an error. It passes an error reason to any attached
.catch()
handlers.
-
resolve(): A function called when the promise is successfully fulfilled. It passes a result value to any attached
- Promises use two callback functions to handle their states:
-
Chaining:
- Promises allow you to chain multiple asynchronous operations together using
.then()
. This enables you to specify a sequence of tasks to execute when the promise is fulfilled.
- Promises allow you to chain multiple asynchronous operations together using
someAsyncFunction()
.then(result => {
// Handle the result
return anotherAsyncFunction(result);
})
.then(finalResult => {
// Handle the final result
})
.catch(error => {
// Handle errors from any of the steps
});
-
Error Handling:
- Promises provide a centralized way to handle errors using
.catch()
. Errors thrown in any.then()
block will propagate down to the nearest.catch()
handler.
- Promises provide a centralized way to handle errors using
someAsyncFunction()
.then(result => {
// Handle the result
throw new Error('An error occurred');
})
.catch(error => {
// Handle the error
});
-
Promise.all():
- You can use
Promise.all()
to wait for multiple promises to fulfill in parallel. It resolves when all the provided promises have resolved, providing an array of their results.
- You can use
const promises = [promise1, promise2, promise3];
Promise.all(promises)
.then(results => {
// Handle the results
})
.catch(error => {
// Handle errors from any of the promises
});
-
Async/Await (ES6 and later):
- ES6 introduced the
async/await
syntax, which simplifies working with promises, making asynchronous code look more like synchronous code.
- ES6 introduced the
async function fetchData() {
try {
const result = await someAsyncFunction();
// Handle the result
} catch (error) {
// Handle errors
}
}
Promises are a crucial part of modern JavaScript and are widely used in web development for handling asynchronous operations such as AJAX requests, file I/O, and more. They promote cleaner, more maintainable code by providing a structured way to deal with asynchronous behavior and errors.
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