promise-sift

ever have a list of promises and you wish to sift through the chaff and obtain the fine grain you're really looking for? or maybe you just want to fire a bunch of ajax requests in parallel and embrace the winners that made it - at the finish line - not bothering about the guys who fainted along the way.

this is promise-sift.

about

the function is extended over the ES6 Promise object like Promise.all and Promise.race.

usage

can be loaded as

• a <script> tag
• npm coming soon

tutorial

the Promise.sift function accepts an array of promises, and an optional error handler function.

basic use

var promises = [
    Promise.resolve('i made it'),
    Promise.reject('i am weak'),
    Promise.resolve('i think i made it')
];

Promise.sift(promises).then(function (results){
    console.log(results); // (2) ["i made it", "i think i made it"]
});

using an error handler

you can pass in a function if you wish to log/do-whatever with the ones that do fail, however the rejection handler still wont be called on the returned promise.

    var promises = [
        Promise.resolve('i made it'),
        Promise.reject('i am weak')
    ];
    function handler(reason) {
        console.log(reason); // executed once
    }
    
    Promise.sift(promises, handler)
    .then(function (results){
        console.log(results); // (1) ["i made it"]
    })
    .catch(function(reason){
        console.log(reason); // never executed
    });

this keeps in line with the idea of not really caring about the fails, and focusing on the passes

when is onRejected called?

1. by standard, when an error is thrown in your fulfillment handler (the first function you pass to then).
2. if the first parameter you pass in (promises) is not an array or is an empty array.