easiest way to return a promise from a function
"promesa" is Spanish for "promise"
var Promesa = require('promesa')
// (Number) => Promise<User>
function getUser(id) {
return Promesa(function () {
if (!(typeof id === 'number' && Number.isFinite(id) && !Number.isNaN(id))) {
throw new TypeError('id must be a number')
}
return {id: id, name: 'Boris Yeltsin'}
})
}
In a real implementation, you would probably have some sort of underlying asynchronous value, like a database lookup.
Promesa
lets you mix and match returning Promise values,
synchronous values, and throwing. As explained in
You're missing the point of promises, Promises/A+ lets
you reason about your code in terms of return
and throw
semantics you already know and love.
Promesa is ideal for making functions which are working with other promises as well as synchronous logic, for example precondition (guard) checking, authorization logic, etc. It assumes that any asynchronous values you're working with are already represented as Promises.
If you need to create promises from other kinds of asynchronous control flow patterns, such as EventEmitters or callback continuations, consider using something like bluebird
's Promise
constructor.
Invokes the function fn
and wraps the result in a Promise.
If fn
returned a Promise, that value will be flattened and returned
(see the Promise Resolution Procedure). If fn
returned a
value, a resolved Promise of that value will be returned. If fn
throws, a rejected Promise will be returned.
$ npm install promesa
From package root:
$ npm install
$ npm test
- jden jason@denizac.org
MIT. (c) MMXIII jden jason@denizac.org. See LICENSE.md