Yahoo Web Search

Search results

1. Top results related to promises in javascript

   • Promises Chaining in JavaScript

     The V8 JavaScript engine, developed by Google, is a high-performance open-source engine designed to execute JavaScript code efficiently. Initially created for the Google Chrome web browser, V8 has become a key component in various applications and platforms, showcasing its versatility.

     V8 employs a Just-In-Time (JIT) compilation technique, translating JavaScript code into machine code right before execution. This approach significantly boosts performance, allowing V8 to dynamically optimize code based on runtime characteristics. The engine incorporates advanced features like inline caching, hidden classes, and adaptive optimizations, contributing to its ability to execute JavaScript rapidly.

     Memory management is handled by V8’s garbage collector, responsible for reclaiming unused resources and ensuring efficient memory utilization. Beyond Chrome, V8 has found widespread adoption, notably in the Node.js runtime environment, where its speed and adaptability have made it a preferred choice for server-side JavaScript applications. Its continual evolution, marked by regular updates and enhancements, solidifies V8’s position as a leading JavaScript engine, influencing the overall performance and responsiveness of JavaScript applications across diverse domains.

     Y

     Check all answers on Geeksforgeeks

     1/5

   • Promises/Fetch in JavaScript: how to extract text from text file

     Top Answer

     Answered May 18, 2018 · 33 votes

     Fetch doesn't return a promise for the text of a response - it returns a promise for a Response object available after headers have been received.

     This is so you can do cool things like:

     • Determine how you want to read the body of the response based on the headers.
     • Stream the response progressively etc.

     If you want the text of the response - you can .text() the Response objects to get a promise for that:

     Promise.all([ fetch('sample.txt').then(x => x.text()), fetch('sample2.txt').then(x => x.text())]).then(([sampleResp, sample2Resp]) => { console.log(sampleResp); console.log(sample2Resp);});-

     Check all answers on Stack Overflow

     2/5

   • Javascript: In promises what is the purpose of resolve and reject?

     Top Answer

     Answered Aug 24, 2021 · 2 votes

     When you create a JS Promise, you expect some task to happen asynchronously. It is possible, that this task can succeed or fail. The success and failure are defined based on what the task is.

     When you create a new Promise, you as the creator must specify what to do when the task is successful or is a failure. To communicate the same to the consumer of the promise resolve/reject come handy.

     So when the consumer uses a then to check the output of the promise. what ever is returned by resolve is given to the consumer.

     When the consumer uses a catch to check the output of the promise. whatever is returned by the reject is given to the consumer.

     import {Promise} from 'es6-promise'--const foo = true;const bar = new Promise((resolve, reject) => { if (foo) { resolve(4); } else { reject(2); }})bar.then((value) => console.log(value)).catch((value) => console.log(value));-

     you can run the above sample by changing the value of foo to true/false and see for yourself what the output is.

     Check all answers on Stack Overflow

     3/5

   • Javascript promises deep in the stack

     Top Answer

     Answered Jun 26, 2015 · 1 votes

     I want to have it async if possible, does it mean I have to make everything in this chain of code consume and return promises?

     Yes. Something that is potentially asynchronous must always return a promise, and must always be consumed as if it was asynchronous (promises enforce this anyway).

     Is the only other alternative to just make a synchronous AJAX request?

     Yes, and you really don't want that.

     Is there a nicer alternative? I'm thinking of C#'s await keyword, but I'm sure other languages have similar functionality.

     In fact, async-await is coming to ECMAScript as well. But it doesn't make anything synchronous, it rather is just syntactic sugar for promises-everywhere.

     Check all answers on Stack Overflow

     4/5

   • Also try

     promises in javascript w3schools	types of promises in javascript
     promises in javascript freecodecamp	callbacks and promises in javascript
     promises in javascript interview questions	promises in javascript examples
     promises in javascript mdn	working with promises in javascript

     5/5

   Show moreShow less

2. developer.mozilla.org › en-US › docsPromise - JavaScript | MDN - MDN Web Docs

   developer.mozilla.org › en-US › docs

   • Cached

   Jun 9, 2024 · Promises in JavaScript represent processes that are already happening, which can be chained with callback functions. If you are looking to lazily evaluate an expression, consider using a function with no arguments e.g. f = () => expression to create the lazily-evaluated expression, and f() to evaluate the expression immediately.

3. www.w3schools.com › Js › js_promiseJavaScript Promises - W3Schools

   www.w3schools.com › Js › js_promise

   • Cached

   Here is how to use a Promise: myPromise.then(. function(value) { /* code if successful */ }, function(error) { /* code if some error */ } ); Promise.then () takes two arguments, a callback for success and another for failure. Both are optional, so you can add a callback for success or failure only.

4. developer.mozilla.org › en-US › docsUsing promises - JavaScript | MDN - MDN Web Docs

   developer.mozilla.org › en-US › docs

   • Cached

   Jun 9, 2024 · A Promise is an object representing the eventual completion or failure of an asynchronous operation. Since most people are consumers of already-created promises, this guide will explain consumption of returned promises before explaining how to create them.

5. javascript.info › promise-basicsPromise - The Modern JavaScript Tutorial

   javascript.info › promise-basics

   • Cached

   Aug 14, 2022 · A promise is a special JavaScript object that links the “producing code” and the “consuming code” together. In terms of our analogy: this is the “subscription list”. The “producing code” takes whatever time it needs to produce the promised result, and the “promise” makes that result available to all of the subscribed code when it’s ready.

6. developer.mozilla.org › en-US › docsHow to use promises - Learn web development | MDN

   developer.mozilla.org › en-US › docs

   • Cached

   May 31, 2024 · Promises are the foundation of asynchronous programming in modern JavaScript. A promise is an object returned by an asynchronous function, which represents the current state of the operation.

7. www.geeksforgeeks.org › javascript-promiseJavaScript Promise - GeeksforGeeks

   www.geeksforgeeks.org › javascript-promise

   • Cached

   May 31, 2024 · JavaScript Promises used to simplify managing multiple asynchronous operations, preventing callback hell and unmanageable code. They represent future values, associating handlers with eventual success or failure, resembling synchronous methods by postponing value delivery until later.

8. www.freecodecamp.org › news › what-is-promise-in-javascript-for-beginnersWhat is a Promise? JavaScript Promises for Beginners -...

   www.freecodecamp.org › news › what-is-promise-in-javascript-for-beginners

   • Cached

   Aug 16, 2021 · JavaScript promises are a very powerful feature that help you run asynchronous code in JavaScript. In most, if not all, interviews for roles which use JavaScript, your interviewer will probably ask a question about promises.

9. www.freecodecamp.org › news › guide-to-javascript-promisesHow Promises Work in JavaScript – A Comprehensive Beginner's...

   www.freecodecamp.org › news › guide-to-javascript-promises

   • Cached

   Jun 13, 2023 · This article is an in-depth guide to promises in JavaScript. You are going to learn why JavaScript has promises, what a promise is, and how to work with it. You are also going to learn how to use async/await—a feature derived from promises—and what a job queue is. Here are the topics we will cover: Why should you care about promises?

10. javascript.info › promise-apiPromise API - The Modern JavaScript Tutorial

    javascript.info › promise-api

    • Cached

    Feb 20, 2022 · The JavaScript language. Promises, async/await. February 20, 2022. Promise API. There are 6 static methods in the Promise class. We’ll quickly cover their use cases here. Promise.all. Let’s say we want many promises to execute in parallel and wait until all of them are ready.

11. web.dev › articles › promisesJavaScript Promises: an introduction | Articles | web.dev

    web.dev › articles › promises

    • Cached

    Dec 16, 2013 · JavaScript Promises: an introduction. Promises simplify deferred and asynchronous computations. A promise represents an operation that hasn't completed yet. Jake Archibald. Developers, prepare yourself for a pivotal moment in the history of web development. [Drumroll begins] Promises have arrived in JavaScript!