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August 19, 2016 08:11
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| //{{ PromisePool | |
| /* Usage: | |
| var promise_pool = new PromisePool([concurrency_limit]); | |
| * concurrency_limit: n of concurrency promices executions | |
| generate a PromisePool | |
| promise_pool.push(fn); | |
| * function: the function to generate promise object | |
| push a function into PromisePool, this functipn will generate promise object | |
| but the real Promise object has *NOT* been generated yet | |
| promise_pool.start(); | |
| generate and execute all Promises in pool base on the concurrency_limit | |
| return a Promise object resolved when all Promises object in pool are resolved/rejected | |
| */ | |
| var PromisePool = function(limit) { | |
| this.queue = []; | |
| this.limit = (limit > 0) ? limit: 10; | |
| }; | |
| PromisePool.prototype = { | |
| constructor: PromisePool, | |
| push: function(fn){ | |
| this.queue.push(fn); | |
| }, | |
| start: function(){ | |
| var that = this; | |
| var p = Promise.resolve(); | |
| var results = []; | |
| var process = function(group){ | |
| return Promise.all(group.map(function(fn){ | |
| return fn(); | |
| })).then(function(r){ | |
| results.push.apply(results, r); | |
| console.log(results.length, 'results merge done'); | |
| return results; | |
| }); | |
| }; | |
| while(that.queue.length) { | |
| p = p.then( | |
| process.bind(that, that.queue.splice(0, that.limit)) | |
| ); | |
| } | |
| return p; | |
| } | |
| }; | |
| ////}} | |
| //{{ Scenario 1 | |
| // Old Scheme | |
| var promise_list = []; | |
| promise_list.push(new Promise(function(resolve, reject){ | |
| // promise 1 | |
| })); | |
| promise_list.push(new Promise(function(resolve, reject){ | |
| // promise 2 | |
| })); | |
| promise_list.push(new Promise(function(resolve, reject){ | |
| // promise 3 | |
| })); | |
| Promise.all(promise_list).then(function(results){ | |
| console.log('all done'); | |
| }); | |
| // New Scheme | |
| var promise_list = new PromisePool(10); | |
| promise_list.push(fnToGeneratePromise1); | |
| promise_list.push(fnToGeneratePromise2); | |
| promise_list.push(fnToGeneratePromise3); | |
| promise_list.start().then(function(results){ | |
| console.log('all done'); | |
| }); | |
| ////}} | |
| //{{ Scenario 2 | |
| /* jQuery included... */ | |
| var getUserData = function(user_id){ | |
| return new Promise(resolve, reject) { | |
| $.get('getUserData.php?user_id='+user_id).then(function(rsp){ | |
| resolve(rsp); | |
| }); | |
| }; | |
| }; | |
| // Old Scheme | |
| var promise_list = []; | |
| promise_list.push(getUserData('user1')); | |
| promise_list.push(getUserData('user2')); | |
| // : | |
| // Skip lots of promise_list.push | |
| // : | |
| promise_list.push(getUserData('user100')); | |
| Promise.all(promise_list).then(function(results){ | |
| console.log('all user data loaded'); | |
| }); | |
| // New Scheme | |
| var promise_list = new PromisePool(10); | |
| promise_list.push(getUserData.bind(this, 'user1')); | |
| promise_list.push(getUserData.bind(this, 'user2')); | |
| // : | |
| // Skip lots of promise_list.push | |
| // : | |
| promise_list.push(getUserData, ['user100']); | |
| promise_list.start().then(function(results){ | |
| console.log('all user data loaded'); | |
| }); | |
| //}} |
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