There are of course legit reasons to force synchronous execution of a promise in js. The most obvious is when require‘ing a file that needs to initialize using some asynchronous stuff, and optimization is not an overriding concern. Seems like the package synchronized-promise seems like it ought to do the trick. In your case (warning … Read more
First difference: Sometimes you don’t want to catch errors at the place they arise, but in the code that uses this function, so you don’t catch them. In that case you can’t substitute then() and finally(). Sometimes you have to clean something up whether there was an error or not (nulling references, clearing timeouts … … Read more
The API for promises requires you to pass a function to the promise constructor. Quoting MDN: new Promise( /* executor */ function(resolve, reject) { … } ); executor – A function that is passed with the arguments resolve and reject. The executor function is executed immediately by the Promise implementation, passing resolve and reject functions … Read more
async/await and promises are closely related. async functions return promises, and await is syntactic sugar for waiting for a promise to be resolved. The only drawback from having a mix of promises and async functions might be readability and maintainability of the code, but you can certainly use the return value of async functions as … Read more
VS Code Debug Console supports top level async/await (https://github.com/microsoft/vscode-js-debug#top-level-await) however the issue might be you’re paused on the breakpoint. if you use await while paused on a breakpoint, you’ll only get a pending Promise back. This is because the JavaScript event loop is paused while on a breakpoint.
When you design a function interface and there are errors to deal with, you have a design choice for how to return errors. If the function is synchronous, you can either return some sentinel value that indicates an error and is easily distinguished from an actual result (often null in Javascript) or you can throw … Read more
Both resolve() and promise() are methods on the jQuery Deferred object. First a snippet from the jQuery documentation about Deferred: One model for understanding Deferred is to think of it as a chain-aware function wrapper. The deferred.then(), deferred.done(), and deferred.fail() methods specify the functions to be called and the deferred.resolve(args) or deferred.reject(args) methods “call” the … Read more
An example of each, using javascript since everybody can read it. Please don’t use this code in production, use a real library, there are plenty of good ones. var a, b, c, async_obj; // assume exist // CommonJS – for reference purposes try { async_obj.asyncMethod(a, b, c, function (error1, result1) { if (error1) { console.error(error1); … Read more
You ask: How can I wait for allPermissions to be loaded before the view renders? To prevent the entire view from rendering, you must use resolve. You don’t have to use the promise library though, since $http returns a promise: var app = angular.module(‘app’); app.config(function ($routeProvider) { $routeProvider .when(“https://stackoverflow.com/”, { templateUrl : ‘template.html’, controller : … Read more
Rule of Thumb Whenever you have a doubt about how to do something with promises – think about the synchronous version. try{ var result = myFn(param); // business logic with result } catch(e) { //error handling logic } This, at least to me looks a lot cleaner than a callback with a first parameter that … Read more