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1. Top results related to promises js

   • Promises Node.js mysql

     Top Answer

     Answered Jan 03, 2017 · 1 votes

     When you call userAgeCheck (userAgeCheck('username')) you pass one argument: A string literal containing the word "username". This gets assigned to randomParam which you then never user rendering it pointless.

     You define a variable at the top of your script: var username = session.uniqueID;

     When you make the query you pass the value of the username variable as the placeholder value for username != ?.

     This is the value of session.uniqueId since it reads the username variable from the wider scope.

     Consequently you get back all the results except those where the username is the username in session.uniqueId.

     If you rename randomParam to username, then you have a new, local variable called username with the value "username".

     Consequently you get back all the results except those where the username is the username is literally username.

     If you want to pass the username as the argument then you need to change userAgeCheck('username') to userAgeCheck(username). i.e. replace the string literal with a variable name.

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     1/5

   • Promises in Node.js

     Introduction: Callback functions are used for Asynchronous events. Whenever any asynchronous event has to be taken place it is generally preferred to use callbacks (if data is not nested or inter-dependent).

     Following is the simplest example where we could visualize how we may use a callback:-

     Example:

     javascript

     module.exports = (x, callback) => {    if (x <= 0)        setTimeout(() =>            callback(new Error("Square dimensions            should be greater than zero: s = " + x),            null), 2000);    else        setTimeout(() =>            callback(null, {                perimeter: () => (4*(x)),                area:() => (x*x)            }), 2000);}-

     What are Promises? A promise is basically an advancement of callbacks in Node.  In other words, a promise is a JavaScript object which is used to handle all the asynchronous data operations. While developing an application you may encounter that you are using a lot of nested callback functions. 

     javascript

     dboper.insertDocument(db, { name: "Test", description: "Test"},    "test", (result) => {        console.log("Insert Document:\n", result.ops);         dboper.findDocuments(db, "test", (docs) => {            console.log("Found Documents:\n", docs);             dboper.updateDocument(db, { name: "Test" },                { description: "Updated Test" }, "test",                (result) => {                    console.log("Updated Document:\n", result.result);                     dboper.findDocuments(db, "test", (docs) => {console.log Found Updated Documents n docs...

     Check all answers on Geeksforgeeks

     2/5

   • Promises in Node.js

     Introduction: Callback functions are used for Asynchronous events. Whenever any asynchronous event has to be taken place it is generally preferred to use callbacks (if data is not nested or inter-dependent).

     Following is the simplest example where we could visualize how we may use a callback:-

     Example:

     javascript

     module.exports = (x, callback) => {    if (x <= 0)        setTimeout(() =>            callback(new Error("Square dimensions            should be greater than zero: s = " + x),            null), 2000);    else        setTimeout(() =>            callback(null, {                perimeter: () => (4*(x)),                area:() => (x*x)            }), 2000);}-

     What are Promises? A promise is basically an advancement of callbacks in Node.  In other words, a promise is a JavaScript object which is used to handle all the asynchronous data operations. While developing an application you may encounter that you are using a lot of nested callback functions. 

     javascript

     dboper.insertDocument(db, { name: "Test", description: "Test"},    "test", (result) => {        console.log("Insert Document:\n", result.ops);         dboper.findDocuments(db, "test", (docs) => {            console.log("Found Documents:\n", docs);             dboper.updateDocument(db, { name: "Test" },                { description: "Updated Test" }, "test",                (result) => {                    console.log("Updated Document:\n", result.result);                     dboper.findDocuments(db, "test", (docs) => {console.log Found Updated Documents n docs...

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     3/5

   • promises exercise in JS

     Top Answer

     Answered Feb 19, 2019 · 1 votes

     Just move result(test) to inside the callback. Like this:

     import express from 'express';import shortUrl from 'node-url-shortener';const router = express.Router();-router.get('/', (req, res) => { res.render('postUrl');})router.post('/test', (req, res) => { const getShortUrl = () => { return new Promise((resolve, reject) => { shortUrl.short('https://google.com', (err, url) => { resolve(url); }); }) } getShortUrl() .then((result) => { console.log('Resultat : ' + result) }) .catch((err) => { console.log('Error : ' + err) }) res.render('getShortUrl');})export { router }

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     4/5

   • JS Promises: Fulfill vs Resolve

     Top Answer

     Answered May 03, 2021 · 28 votes

     Indeed, the resolve callback does not imply that the promise will be fulfilled.

     The terms fulfilled, rejected, pending, settled, resolved and locked-in are defined in the EcmaScript2015 specs, 25.4 Promise Objects:

     Any Promise object is in one of three mutually exclusive states: fulfilled, rejected, and pending:

     • A promise p is fulfilled if p.then(f, r) will immediately enqueue a Job to call the function f .
     • A promise p is rejected if p.then(f, r) will immediately enqueue a Job to call the function r .
     • A promise is pending if it is neither fulfilled nor rejected.

     A promise is said to be settled if it is not pending, i.e. if it is either fulfilled or rejected.

     A promise is resolved if it is settled or if it has been “locked in” to match the state of another promise. Attempting to resolve or reject a resolved promise has no effect. A promise is unresolved if it is not resolved. An unresolved promise is always in the pending state. A resolved promise may be pending, fulfilled or rejected.

     A short overview, where I will use the term "autonomous" as the opposite of "locked in". They are the two possible values for a promise's dependency situation:

     * The thenable is now in control over the future state of our promise object.

     The above quote mentions that a promise is locked-in to match the state "of another promise", but more precisely that "other promise" could also be a non-promise "thenable" as can be seen in the steps 11 and 12 of the process description in 25.4.1.3.2

     • If IsCallable(thenAction) is false, then      a. Return FulfillPromise(promise, resolution).
     • Perform EnqueueJob ( "PromiseJobs", PromiseResolveThenableJob, «‍promise, resolution, thenAction»)

     A demo of resolve being called with a thenable, which in turn triggers a rejection:

     const thenable = { // Could be a promise object, but does not have to be then(success, fail) { setTimeout(() => fail("gotcha!"), 1000); }}const p = new Promise((resolve, reject) => { console.log("1. The promise is created as pending"); setTimeout(() => { resolve(thenable); console.log("2. It's resolved with a thenable; it's not yet settled"); }, 1000);});p.catch(err => console.log(`3. It's settled as rejected with error message "${err}"`));

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     5/5

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

   developer.mozilla.org › en-US › docs

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   May 31, 2024 · A Promise is a proxy for a value not necessarily known when the promise is created. It allows you to associate handlers with an asynchronous action's eventual success value or failure reason.

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

   Mar 21, 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

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   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”.

6. 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?

7. www.w3schools.com › jsref › jsref_obj_promiseJavaScript Promise - W3Schools

   www.w3schools.com › jsref › jsref_obj_promise

   • Cached

   JavaScript Promise Object. Previous Next . The Promise Object represents the completion or failure of an asynchronous operation and its results. A Promise can have 3 states: Example. // Create a Promise Object. let myPromise = new Promise (function(myResolve, myReject) { let result = true; // Code that may take some time goes here.

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

   developer.mozilla.org › en-US › docs

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   May 31, 2024 · Promises are the foundation of asynchronous programming in modern JavaScript. They make it easier to express and reason about sequences of asynchronous operations without deeply nested callbacks, and they support a style of error handling that is similar to the synchronous try...catch statement.

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

   javascript.info › promise-api

   • Cached

   Feb 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. For instance, download several URLs in parallel and process the content once they are all done. That’s what Promise.all is for.

10. www.javascripttutorial.net › es6 › javascript-promisesJavaScript Promises - JavaScript Tutorial

    www.javascripttutorial.net › es6 › javascript-promises

    • Cached

    A promise is an object that encapsulates the result of an asynchronous operation. A promise starts in the pending state and ends in either a fulfilled state or a rejected state. Use then() method to schedule a callback to be executed when the promise is fulfilled, and catch() method to schedule a callback to be invoked when the promise is rejected.

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

    web.dev › articles › promises

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    Dec 16, 2013 · JavaScript Promises: an introduction. On this page. Browser support and polyfill. What's all the fuss about? Events aren't always the best way. Promise terminology. Promises arrive in JavaScript! Promises simplify deferred and asynchronous computations. A promise represents an operation that hasn't completed yet. Jake Archibald.