js-executor

executor.js

module.exports= (function(){
    'use strict';

    var Executor= function(opts){
        opts || (opts= {});

        this.nactives= opts.nactives || 10;
        this.actives= [];
        this.all= [];
    };

    Executor.prototype.submit= function(fun, ctx){
        var that= this;
        var waiter= function(resolve, reject){
            if(that.actives.length >= that.nactives)
            {
                console.log('  Wait next time. (actives = ' + that.actives.length + ')');
                return setTimeout(function(){
                    waiter.call(that, resolve, reject);
                }, 0);
            }

            console.log('  execute (actives = ' + that.actives.length + ')');
            that.actives.push(true);
            fun.call(ctx, resolve, reject);
        };
        var popper= function(){
            that.actives.pop();
        }
        var promise= new Promise(waiter);
        promise.then(popper, popper);
        this.all.push(promise);
        return promise;
    };

    Executor.prototype.wait= function(){
        return Promise.all(this.all);
    };

    return Executor;
})();

test.js

(function(){
    'use strict';

    var Executor= require('./executor.js');

    var executor= new Executor({
        nactives: 4
    });

    for(var i= 0; i < 20; ++i)
    {
        console.log('submitting');
        executor.submit(function(resolve, reject){
            var fs= require('fs');
            fs.readFile('./executor.js', function(){
                resolve();
                console.log('  done');
            });
        });
    }

    console.log('waiting');
    executor
        .wait()
        .then(function(){
            console.log('all done');
        })
        .catch(function(e){
            console.log('Something wrong', e);
        })
    ;
})();