The following should work: var request = Promise.promisify(require(“request”)); Promise.promisifyAll(request); Note that this means that request is not a free function since promisification works with prototype methods since the this isn’t known in advance. It will only work in newer versions of bluebird. Repeat it when you need to when forking the request object for cookies. … Read more
2017 update: First, for readers coming today – here is a version that works with Node 7 (4+): function enforceFastProperties(o) { function Sub() {} Sub.prototype = o; var receiver = new Sub(); // create an instance function ic() { return typeof receiver.foo; } // perform access ic(); ic(); return o; eval(“o” + o); // ensure … Read more
I don’t think there are any libraries to do this, but it’s actually quite simple to implement yourself: function sequential(fn) { // limitConcurrency(fn, 1) let q = Promise.resolve(); return function(x) { const p = q.then(() => fn(x)); q = p.reflect(); return p; }; } For multiple concurrent requests it gets a little trickier, but can … Read more
NO you can’t get the data synchronously out of a promise like you suggest in your example. The data must be used within a callback function. Alternatively in functional programming style the promise data could be map()ed over. If your are OK using async/await (you should it’s awesome) then you can write code that looks … Read more
This will be straightforward if you can use async/await: // Make sure that this code is inside a function declared using // the `async` keyword. let currentProduct; for (let i = 0; i < products.length; i++) { currentProduct = products[i]; // By using await, the code will halt here until // the promise resolves, then … Read more
I would recommend using standard JS promises built into the language over an additional library dependency like Bluebird. If you’re using Node 10+, the Node.js docs recommend using util.promisify which returns a Promise<{ stdout, stderr }> object. See an example below: const util = require(‘util’); const exec = util.promisify(require(‘child_process’).exec); async function lsExample() { try { … Read more
Does there exist a situation where it would be necessary (or just better somehow) to use a deferred? There is no such situation where a deferred is necessary. “Better” is a matter of opinion so I won’t address that here. There’s a reason that the ES6 promise specification does not have a deferred object. You … Read more
Let’s look at a simple recursive function that expresses our program at a high level let RUNNING = true const main = async (elem, color = Color ()) => RUNNING ? delay (color, FPS) .then (effect (color => setElemColor (elem, color))) .then (color => main (elem, stepColor (color))) : color We’ve done a little wishful … Read more
cast can be translated to resolve. defer should indeed not be used. You’d create your loop only by chaining and nesting then invocations onto an initial Promise.resolve(undefined). function promiseWhile(predicate, action, value) { return Promise.resolve(value).then(predicate).then(function(condition) { if (condition) return promiseWhile(predicate, action, action()); }); } Here, both predicate and action may return promises. For similar implementations also … Read more
The 2.0 branch documentation contains a better promisification guide https://github.com/petkaantonov/bluebird/blob/master/API.md#promisification It actually has mongodb example which is much simpler: var Promise = require(“bluebird”); var MongoDB = require(“mongodb”); Promise.promisifyAll(MongoDB);