promise

问题 There's a snippet of code that I cannot seem to understand. There's a function that is declare empty at first: let dCredentials = (credentials: any) => {} Then this variable is later reasignned in a function later called: return new Promise((resolve, _) => (dispatchCredentials = resolve)) What does the second code do? Does it return anything after someone uses .then in the promise? 回答1: If you get a reference to the resolve function to outside the promise, then you can resolve it at any point

问题 How to chain ES6 nested Promises with each Promise in the nesting having then and catch blocks? For example, what will be the Promise then and catch blocks chaining implementation equivalent for following nested AJAX calls implementation handled by success and error callbacks, considering every API call returns a Promise ? $.ajax({ url: 'url1', success: function() { console.log('URL1 call success'); $.ajax({ url: 'url2', success: function() { console.log('URL2 call success'); }, error

问题 const setTimeoutProm = (delay) => new Promise(res => setTimeout(() => res(delay),delay)) I want to do something like, const asyncOpr = (delay) => { return new Promise((resolve, reject) => { //update delay for some reason. const updatedDelay = delay * 2; setTimeoutProm(updatedDelay).then(res => { resolve(res); }).catch(err => {}) }) } asyncOpr(2000).then(() => alert("resolved")) //this works This works as expected, but I am not sure if this is correct way of doing this or is there any better

问题 I am using a javascript file that runs transactions via node. (node create-transaction.js in the terminal returns 200 :) Right now I have a post request that posts something called opaquedata from my client side to my api in my routes file and it works like charm! My only questions is how do i replace the static opaque data inside the boilerplate create-transaction.js file as seen below, with the dynamic opaqudata I am receiving in my api post request. Then how do I get it to run the file

问题 I'm fetching text from a Dictionary API and I can't quite figure out why my code returns a pending promise. However logging the value returns the intended text. Here is my code, const getWord = (difficulty) => { const fetchParameters = api + "?difficulty=" + difficulty let outputWord = fetchWord(fetchParameters).then(value => { console.log(value) // ->Logs intended text return value }) return outputWord // -> Returns Pending Promise } async function fetchWord(fetchParams) { const response =

问题 Is it a good practice to convert the observable object to a promise since observable can be used in almost all the occasions instead of promise? I've started to learn angular recently and come across the below code snippet in a new project(Angular 5) at my workplace. This code snippet is used to load a list of data such as a customer list. This customer list data set is received as a one time action, not as a stream. Therefore it has no technical limitation to use promise. But I would like to

问题 I have a method that I am calling on the onsubmit event in the form tag. So I need a true or false to be returned from the method. I use an API to retrieve data, and according to the response from the API, I return true or false. But because it is an async function thats running, I cant get it right to wait for the response from the API, analyze it and then return my decision. Any ideas on how I could solve this problem function GetPolygonID() { document.getElementById("displayerror")

问题 I have a system that wants to create many folders in dropbox using the api, however i appear to attempt to create all the folders at once which causes errors to be generated, stating that i am performing too many write operations from dropbox. My code is as follows and first uses reduce to create multiple promises which i thought were chained. In these promises the function add is called, which uploads the case to mongodb and then creates a dropbox folder for it, however this results in

问题 If I have the following code new Promise(res => res(1)) .then(val => console.log(val)) is this equivalent to let val = await new Promise(res => res(1)) console.log(val) I know one difference is that I have to wrap the second one in an async function, but otherwise are they equivalent? 回答1: Because your promise always resolves (never rejects), they are equivalent. You could also do: Promise.resolve(1).then(val => console.log(val)); Keep in mind that a major difference with await (besides it

问题 If I have the following code new Promise(res => res(1)) .then(val => console.log(val)) is this equivalent to let val = await new Promise(res => res(1)) console.log(val) I know one difference is that I have to wrap the second one in an async function, but otherwise are they equivalent? 回答1: Because your promise always resolves (never rejects), they are equivalent. You could also do: Promise.resolve(1).then(val => console.log(val)); Keep in mind that a major difference with await (besides it