如何重用异步回调函数？

Question

我在两个具有相同回调函数的函数中使用async.parallel .在第二个函数（two()）中添加了第三个函数作为加法函数

function one(){
var testuser = 1;
 async.parallel([onefunction, secondfunction], function(err, result){...})
}

function two(){
var testuser = 2;
async.parallel([onefunction, secondfunction, thirdfunction], function(err, result){...})
}

function onefunction(callback){....code with testuser......}
function twofunction(callback){....code with testuser......}
function thirdfunction(callback){....code with testuser......}

问：如何访问onefunction、secondfunction 和thirdfunction 中的testuser 值。

现在我得到 undefined err。我也尝试了正常的参数传递逻辑onefunction(testuser)，但它不起作用。

我想在多个情况下使用onefunction、twofunction...我该怎么做？

Answer 1

正如@Felix 建议的那样，

function one(){
var testuser = 1;
 async.parallel([onefunction, secondfunction], function(err, result){...})
}

    function two(){
    var testuser = 2;
    async.parallel([
       callback => onefunction(testuser, callback), 
       callback => twofunction(testuser, callback), 
       callback => thirdfunction(testuser, callback)], function(err, result){...})
    }

    function onefunction(callback){....code with testuser......}
    function twofunction(callback){....code with testuser......}
    function thirdfunction(callback){....code with testuser......}

Answer 2

这是我如何访问onefunction、secondfunction 等中的testuser 值。
代码：

var async = require('async');

function one(){
    var testuser = 1;
    //You can bind a context here; remember to pass the context i.e. null for this, otherwise it won't work as expected.
    async.parallel({one_func:onefunction.bind(null,testuser), two_func:twofunction.bind(null,testuser)}, function(err, result){
        console.log("In one()");
        console.log("err",err);
        console.log("result",result); //result array with all task's results e.g. one_func, two_func
        console.log("testuser",testuser);
 })
}

function onefunction(testuser,cb){
    console.log('onefunction');
    return cb(null,{"testuser":testuser});
}

function twofunction(testuser,cb){
    console.log('twofunction');
    return cb(null,{"testuser":testuser});
}

one();

更新：回答您在标题中关于重用回调的另一个问题。
您可以重用命名函数作为回调吗？
示例代码：

function one(){
    var testuser = 1;
    async.parallel({one_func:onefunction.bind(null,testuser), two_func:twofunction.bind(null,testuser)},calback)
}

function calback (err, result){
        console.log("calback"); //You can reuse this named function as callbacks
        console.log("err",err);
        console.log("result",result);
 }