promise

问题 I found the following code in a project, that I do not understand.: get(key, store = null) { if (!key) { return new Error('There is no key to get!'); } let dbstore = this.localforage; if (store !== null) { dbstore = store; } return dbstore .getItem(key) .then(function(value) { return value; }) .catch(function(err) { return new Error('The key (' + key + ") isn't accessible: " + err); }); } Why return new Error('There is no key to get!'); instead of throw new Error('There is no key to get!'); ?

问题 I found the following code in a project, that I do not understand.: get(key, store = null) { if (!key) { return new Error('There is no key to get!'); } let dbstore = this.localforage; if (store !== null) { dbstore = store; } return dbstore .getItem(key) .then(function(value) { return value; }) .catch(function(err) { return new Error('The key (' + key + ") isn't accessible: " + err); }); } Why return new Error('There is no key to get!'); instead of throw new Error('There is no key to get!'); ?

问题 I'm trying to use the async module (v3) and especially the async.mapLimit method to submit a limited number of parallel asnychronous requests. This works well with callbacks in the following (simplified) sample code: async = require('async'); async.mapLimit(['1','2','3','4','5'], 3, function(num, callback){ setTimeout(function(){ num = num * 2, console.log(num); callback(null, num); }, 4000); },function(err, results){ console.log(results); }); As result I get the single values and finally the

问题 Why is vue-router giving me this error? To be clear, the login flow works as intended but I want to a) get rid of the errro and b) understand why the error is happening. Error: Uncaught (in promise) Error: Redirected from "/login" to "/" via a navigation guard. Login flow start logged out, but enter a URL that requires auth (i.e. anything besides "/login") get redirected to "/login" (as expected). login successfully get redirected to starting Url from step #1, except with the above error.

问题 I'm using babel-preset-env (Babel 6) and I can't find out how to disable the "promise" transpilation. I tried to use: { "presets": [ [ "env", { "exclude": ["transform-async-to-generator", "es6.promise"] } ] ], "plugins": [ "transform-object-rest-spread", "transform-class-properties", [ "fast-async", { "spec": true, "compiler": { "promises": true, "generators": false } } ] ] } and, while it doesn't throws any errors (unlike it happens when an invalid option is passed), it still transpiles

问题 I'm using babel-preset-env (Babel 6) and I can't find out how to disable the "promise" transpilation. I tried to use: { "presets": [ [ "env", { "exclude": ["transform-async-to-generator", "es6.promise"] } ] ], "plugins": [ "transform-object-rest-spread", "transform-class-properties", [ "fast-async", { "spec": true, "compiler": { "promises": true, "generators": false } } ] ] } and, while it doesn't throws any errors (unlike it happens when an invalid option is passed), it still transpiles

问题 I'm seeing this behavior in Node and Chrome: setTimeout(()=>{ console.log('timeout') }, 0) Promise.resolve().then(()=>{ console.log('promise') }) console.log('sync') // output order: // sync // promise // timeout My question is, is this consistent behavior? I.e, according to spec, does a then or await on a memoized/already resolved promise always fire before setTimeout(fn, 0) ? I want to use this in something like the following, returning one thing if I have a memoized result in my promise

问题 If i hit /route2 , i get reponse 15s later,but during that time /route1 gives response immediately. Shouldn't server wait for 15s and then give the response to /route1. I read https://medium.com/@cinish/nodejs-multiple-client-requests-694d6353218b but could not the idea. What i understood is as /route2 is hit console P1 then as there is setTimeout() ,put it in external thread,then console P2 then as setTimeout() ,put it in external thread.Now wait for setTimeouts() to finish. (At this time

问题 If i hit /route2 , i get reponse 15s later,but during that time /route1 gives response immediately. Shouldn't server wait for 15s and then give the response to /route1. I read https://medium.com/@cinish/nodejs-multiple-client-requests-694d6353218b but could not the idea. What i understood is as /route2 is hit console P1 then as there is setTimeout() ,put it in external thread,then console P2 then as setTimeout() ,put it in external thread.Now wait for setTimeouts() to finish. (At this time

问题 I have a JSON object, which includes other objects and list of objects. Have to write a function, which iterates through all properties of objects as well as object within object and list of objects and replace null with an empty string. As it is loop inside loop, I need to implement deferred so sequential processing. I tried many ways, but failed. Anyone please help. function ValidateObject(result) { var aObj = result.A; aObj = VerifyForNull(aoBJ); var bObj = result.B; bObj = VerifyForNull