node async模块 waterfall+queue使用

async_test.js

var async = require('async');
var http = require('http');

function getPage(callback) {
    http.get('http://www.baidu.com', function(res) {
        var buffers = [];
        var size = 0;
        res.on('data', function(buffer) {
            buffers.push(buffer);
            size += buffer.length;
        });
        res.on('end', function() {
            var buffer = new Buffer(size);
            var pos = 0;
            for (var i = 0; i < buffers.length; i++) {
                buffers[i].copy(buffer, pos);
                pos += buffers[i].length;
            }
            callback(null, buffer);
        });
    });
}

function printPage(buffer, callback) {
    console.log(buffer.toString());
    callback(null, 'done');
}

var q = async.queue(function (task, callback) {
    //console.log('hello ' + task.name);
    async.waterfall([getPage, printPage], function(err, results) {
        callback();
    });
    
}, 2);

// assign a callback
q.drain = function() {
    console.log('all items have been processed');
};

q.push([{name: 'baz'},{name: 'bay'},{name: 'bax'}], function (err) {
    console.log('finished processing bar');
});