将函数传递给Node.js中的嵌套回调

Question

I'm trying to get my head around how to perform a couple of async request but passing the a function to the callback. Like below in my GetPosts(), I'm passing a function. So my question is how do I handle the callbacks in the async.series function at the same time as being able to pass in a function to deal with callback from these callbacks from the series. At the moment I'm calling cb but not the "callback", but not sure what the work around is. Does that make sense?

var request = require("request");
var async = require("async");

Context.prototype.GetPosts = function (params, cb) {
    async.series({
        one: function (callback) {
            request("http://jsonplaceholder.typicode.com/posts/1", function (error, response, body) {
                if (!error && response.statusCode == 200) {
                    return cb(body);
                }
                cb(null, result);
            });
        },
        two: function (callback) {
            request("http://jsonplaceholder.typicode.com/posts/1", function (error, response, body) {
                if (!error && response.statusCode == 200) {
                    return cb(body);
                }
                cb(null, result);
            });
        }
    },
    function (err, results) {
    });
};

var params = new Params("MyPosts");

Context.GetPosts(params, function (cb) {
    console.log("Response: " + cb);
});

Thank you in advance.

Answer 1

You call callback where you're now calling cb, to let Async know it's time to move on, and then you call cb in the final callback at the bottom of the GetPosts function, as that fires when the entire series is done.

Pass the errors on, so you can handle them in the callback for GetPosts

var request = require("request");
var async   = request("async");

Context.prototype.GetPosts = function (params, cb) {
    async.series({
        one: function (callback) {
            request("http://jsonplaceholder.typicode.com/posts/1", function (error, response, body) {
                if (error) return callback(error, null);
                if (response.statusCode == 200) return callback(null, body);
                return callback('err', null);
            });
        },
        two: function (callback) {
            request("http://jsonplaceholder.typicode.com/posts/1", function (error, response, body) {
                if (error) return callback(error, null);
                if (response.statusCode == 200) return callback(null, body);
                return callback('err', null);
            });
        }
    },
    function (err, results) {
        if (err) {
            return cb(err, null);
        } else {
            return cb(null, results);
        }
    });
};

var ctx = new Context();

ctx.GetPosts(new Params("MyPosts"), function (err, data) {
    if (err) {
        // handle error
    } else {
        console.log("Response: " + data);
    }        
});