We will find the 5 latest questions for each programming language. Stack overflow practical search example with Axios #įor this practical example, we will use the Axios npm library to make the calls to the Stack Exchange Search API. For this, we will use the StackExchange Search API. We will search Stackoverflow questions with the language name in the title of the question. We will use JavaScript Promise.all with a code example. Subsequently, we will see how to use Promise.all in action. Now you have been advised to use the powers of JavaScript Promise.all responsibly. The API might rate limit the calls and throttle the requests resulting in 403s. ![]() The caveat here is to be careful using it, especially with external resources like API or database calls.Īs the promises sent in as an iterable to the Promise.all are run concurrently, be very careful when using it for external resources like an API. Rather than doing it one by one, Promise.all will fetch it concurrently, it may speed up the task by 3 times. So you can put the fetching 3 user profiles promises in an array and pass it to the Promise.all and await on it. For example, if you have to get user profiles for 3 users, that is an independent task. So, it would be safe to say that Promise.all will take as long a the slowest promise to resolve and fail fast as soon as the first promise in the array fails. In contrast, Promise.race would have been resolved as soon as the first promise was resolved. As seen above, only when the last promise in the iterable promises is fulfilled does the aggregate result of Promise.all get resolved. This is taken from the Promise.all visualized page showing how does JavaScript Promise.all works. Let’s look at the case when all the input promises of a Promise.all pass, how would it look visually: If any one of the input promises gets rejected, the returned promise rejects immediately. This returned Promise will only resolve if all the input promises have been resolved. JavaScript’s Promise.all() method takes in a parameter of iterable promises runs them concurrently then returns a single Promise that resolves to an array of results of the input promises. In the next section, we will look into why use the JavaScript Promise all method. ![]() ![]() There are ways to run promises concurrently like Promise.race, Promise.any and Promise.all. fulfilled: this state means that the operation has been completed with success.pending: which is the initial state when the promise is created.A promise can be in one of these three states: In JavaScript, it is an object whose value is not known now when created, but it will be known when the async action comes back with a value possibly a successful one. If you want to know how async JavaScript works this talk about the event loop is a gem.Īs the name points out, a Promise is an object that will eventually have a value on the completion or failure of the asynchronous process. Promise or Future (also called Delay and deferred) are not exclusive to JavaScript, other programming languages that support async processing or threads also have it. Call StackOverflow API concurrently with Promise.all.Call Stackoverflow sequentially with loop.Stack overflow practical search example with Axios.In this post, we will dissect how JavaScript Promise.all function works visually and with a real-life code example, let’s get started! Table of contents # Async execution and promises are not easy to understand in any language and JavaScript is no exception.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |