angular-q-limit

Adds $q.allLimit() method to Angular which allows $q.all() batching.

One of my biggest gripes with the Angular $q implementation is if you have a lot of Promises to resolve these can quickly overwhelm the Browser / Server.

This module adds the $q.allLimit() function which provides the same functionality as the regular $q.all() function but only allows a limited number of Promises to run at once.

NOTES:

• Unless otherwise specified the default limit for .allLimit() calls is 1.
• The limit number can be anywhere within the list of promises. e.g. $q.allLimit(3, promises...) or $q.allLimit(promises..., 3)
• This module will also fire a progress notification if you need to monitor how many promises have completed

Install

1. Add a reference to the script somewhere in your HTML:

<script src="/vendors/angular-q-limit/angular-q-limit.js"></script>

1. Then add the module to your Angular header file:

var app = angular.module('app', [
    'angular-q-limit',
]);

1. You can now use the limiter in code as part of the regular $q library:

app.controller(function($scope, $q) {
 
    // Run lots of things but only 3 at a time
    $q.allLimit(3, [
        // Lots of promises here ///
    ])
        .then(function(data) {
            // Done!
        }, function(err) {
            // One promise died!
        }, function(progress) {
            // Progress updates! (progress will equal {completed: Number, count: Number, limit: Number})
        });
 
});

Examples

Each of the following examples assumes SomeModel is a Promise based structure like $http or ngResource. Each of these would perform some time consuming task like transmitting large quantities of data to or from the server.

Defined promises

This example runs 3 defined promise limited to 1 item of concurrency. The example shown only lists three promises but this can be extended indefinitely with the guarantee that only 2 items can run at once.

// Load different models and set $scope.data{1,2,3} to the return value
// Only allow two Promises to run at once
 
$q.limitAll(2, [
 
    SomeModel1.query().$promise
        .then(data => $scope.data1 = data),
 
    SomeModel2.query().$promise
        .then(data => $scope.data2 = data),
 
    SomeModel3.query().$promise
        .then(data => $scope.data3 = data),
 
    // More promises here ...
 
]).then(function() { // All done // }});

Dynamic promise creation

This example uses a dynamic array of items, creating a promise for each and finally executing them via $q.limitAll() with a maximum of 3 items running concurrently.

var stuff = [ // Very big array of IDs to request // ];
 
$q.allLimit(3,
    stuff.map(function(item) {
        return SomeModel.get({id: item}).$promise;
    }),
});