es6-promise

问题 I would like to execute a set of promises using Promise.all(). My approach is to put these promises in an array and then pass the array to Promise.all(). However, I find that the promises start executing as soon as they are declared and do not even wait for Promise.all to be called. Why is this happening and how can I have the promises only execute upon calling Promise.all()? let promiseArray = []; const values = [1, 2, 3, 4, 5]; values.forEach((value)=>{ promiseArray.push( new Promise(

问题 I would like to execute a set of promises using Promise.all(). My approach is to put these promises in an array and then pass the array to Promise.all(). However, I find that the promises start executing as soon as they are declared and do not even wait for Promise.all to be called. Why is this happening and how can I have the promises only execute upon calling Promise.all()? let promiseArray = []; const values = [1, 2, 3, 4, 5]; values.forEach((value)=>{ promiseArray.push( new Promise(

问题 I create two promises, but I do not run the then method on those promises. Yet once the promise objects go out of scope, the promise code runs as if .then was called. How is a Promise settled without a call to the .then method? I am asking because I would like to load an array with Promise objects and then run the promises in sequence. function promises_createThenRun() { const p1 = createPromise1(); const p2 = createPromise2(); console.log('before hello'); alert('hello'); console.log('after

问题 I have been reading up on async/await in node.js. I have learnt that the await keyword waits for a promise to be resolved, or throws an exception if it was rejected. I have also learnt that every function that wants to use await needs to be marked async . However, what does it mean for a function to be marked async ? All the resources and blog posts I was able to find seem to explain await in great detail, but ignore the concept of an async function, or briefly gloss over it. For instance,

问题 I have a a object that when I'm printing that it's returning Promise <Pending> (I've checked the type of getRateable and it is object) getRateable = getRateableEntitiesTx(tx, hashtagList); I can't have access to the value by this : getRateableEntitiesTx(tx, hashtagList).then((res) => {return res}) If it's a Promise why it's not returning the res properly? Thanks in advance for help 回答1: You can't return the value from an async function because the function returns before the value has been

问题 I've read similar posts, but none quite hit on the head how to do this correctly. I understand Promises and how they are typically created with success and failure listeners waiting to be triggered to either resolve or reject. What I don't understand is when I'm calling an API method that takes a success and failure callback as parameters - how do I determine which callback is being triggered so I can then have it resolved or rejected? For example with this Web API and considering the

问题 I've read similar posts, but none quite hit on the head how to do this correctly. I understand Promises and how they are typically created with success and failure listeners waiting to be triggered to either resolve or reject. What I don't understand is when I'm calling an API method that takes a success and failure callback as parameters - how do I determine which callback is being triggered so I can then have it resolved or rejected? For example with this Web API and considering the

问题 I've got an angular HttpInterceptor and I need to call an encryption method that's defined like so: private async encrypt(obj: any): Promise<string> { I'm not sure how to handle this in the HttpInterceptor though: intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> { const modified = req.clone({ body: this.encrypt(req.body) }); return next.handle(modified).pipe( I'm not sure how to tie the two of those together so that I can call the encrypt method properly from

问题 I've got an angular HttpInterceptor and I need to call an encryption method that's defined like so: private async encrypt(obj: any): Promise<string> { I'm not sure how to handle this in the HttpInterceptor though: intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> { const modified = req.clone({ body: this.encrypt(req.body) }); return next.handle(modified).pipe( I'm not sure how to tie the two of those together so that I can call the encrypt method properly from

问题 I've got an angular HttpInterceptor and I need to call an encryption method that's defined like so: private async encrypt(obj: any): Promise<string> { I'm not sure how to handle this in the HttpInterceptor though: intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> { const modified = req.clone({ body: this.encrypt(req.body) }); return next.handle(modified).pipe( I'm not sure how to tie the two of those together so that I can call the encrypt method properly from