Promise all results of a collection of promises whether they are resolved OR rejected.
Often we want to accomplish several asyncrounous tasks at once. Usually,
Promise.all does what we want, but it has a couple limitations:
- Rejections only provide rejection reason. Sometimes you want the data from Promises that did resolve, or you want to know specifically which items failed and which succeeded.
- Requires a numerically indexed array.
It's often more conveniant to label our parralel jobs with object keys than a
flat index.
promise-resultswill handle keyed objects or arrays.
var resultsOf = require('promise-results');
var pack = {};
pack.a = Promise.resolve(2);
pack.b = pack.a.then(function (r) {
return new Promise(function (resolve, reject) {
setTimeout(function() {
resolve(r + 1);
}, 10);
})
});
pack.c = 42
pack.d = new Promise(function (resolve, reject) {
setTimeout(function() {
reject(new Error('Some random failure'));
}, 10);
});
resultsOf(pack).then(function (results) {
assert(results.a === 2);
assert(results.b === 3);
assert(results.c === 42);
assert(results.d instanceof Error);
});If you just want to use objects, but want to keep Promise.all single
rejection pattern, you can use the allKeys function instead.
var allKeys = require('promise-results/allKeys');
var pack = {};
pack.a = Promise.resolve(2);
pack.b = a.then(function (r) {
return new Promise(funciton (resolve, reject) {
setTimeout(function() {
resolve(r + 1);
}, 10);
})
});
pack.c = 42
pack.d = new Promise(function (resolve, reject) {
setTimeout(function() {
reject(new Error('Some random failure'));
}, 10);
});
allKeys(pack).catch(function (err) {
assert(err instanceof Error);
});If you like having a defined reject route, but still want access to
your partial results and rejections. You can use resultSet.
var results = require('promise-results/resultSet');
var pack = {};
pack.a = Promise.resolve(2);
pack.b = a.then(function (r) {
return new Promise(funciton (resolve, reject) {
setTimeout(function() {
resolve(r + 1);
}, 10);
})
});
pack.c = 42
pack.d = new Promise(function (resolve, reject) {
setTimeout(function() {
reject(new Error('Some random failure'));
}, 10);
});
results(pack).catch(function (result) {
assert(result.d instanceof Error);
});
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