GeneratorとPromiseの勉強ということでオレオレなco moduleを実装

00. Resource.js

//Dummy resource
module.exports = {
    open: function() {

        var res = {
            read: function() {
                return new Promise(function(_resolve, _reject) {
                    setTimeout(function() {
                        _resolve('hogeeee');
                        //_reject('read error!');
                    }, 1000);
                });
            },
            close: function() {
                console.log('Resource is closed.');
            }
        };

        return new Promise(function(resolve, reject) {
            setTimeout(function() {
                console.log('Resource is opened.');
                resolve(res);
                //reject('open error!');
            }, 1000);
        });
    }
};

01. co.js

module.exports = function(gfn) {

    var g = gfn();

    var a = function(v) {
        var b = g.next(v);
        if (!b.done) {
            return b.value.then(a);
        } else {
            return b.value;
        }
    };

    return Promise.resolve().then(a);
};

02. main.js

var Resource = require('./00. Resource');
var co = require('./01. co');

co(function* () {

    var res = yield Resource.open('path');

    try {
        var result = yield res.read();
        console.log(result);
    } finally {
        res.close();
    }

})
.catch(function(err) { console.error(err); });