nodejs第三方模块async异步流程控制模块

npm安装

async 官方文档：

https://caolan.github.io/async/

学习async 异步控制模块；最好的还是看官方文档，因为模块版本更新快！

控制流方法

auto :

auto(tasks, concurrencyopt, callbackopt)

1. tasks中的每个函数，可以根据它自身的要求来定义执行的顺序。每个函数可以选择在他执行之前必须要执行的函数；当然也可以不指定。

2. 如果tasks中的一个函数发生了错误，产生了错误信息err ;那么tasks这个执行序列就会停止，其他还没执行的函数就不执行，依赖它先执行的函数们就更不会执行了。并且callback会立即被调用参数就是err。

3. tasks中的函数，参数要么是一个，那么是两个；如果它有依赖其他函数那么第一个参数是依赖函数的结果集；如果没有依赖，那么它只有一个参数就是callback

例子：

var async = require('async');
var fs = require('fs');
var callback = function (err, results) {
    console.log(results);
};
async.auto({
    // this function will just be passed a callback
    readData: async.apply(fs.readFile, 'data.txt', 'utf-8'),
    showData: ['readData', function(results, cb) {
        // results.readData is the file's contents
        // ...

        cb(null,results);
    }]
}, callback);

async.auto({
    get_data: function(callback) {  //最后那个参数就是 callback
        console.log('in get_data');
        // async code to get some data
        callback(null, 'data', 'converted to array');
    },
    make_folder: function(callback) {
        console.log('in make_folder');
        // async code to create a directory to store a file in
        // this is run at the same time as getting the data
        callback(null, 'folder');
    },
    write_file: ['get_data', 'make_folder', function(results, callback) {
        console.log('in write_file', JSON.stringify(results));
        // once there is some data and the directory exists,
        // write the data to a file in the directory
        callback(null, 'filename');
    }],
    email_link: ['write_file', function(results, callback) {
        console.log('in email_link', JSON.stringify(results));
        // once the file is written let's email a link to it...
        // results.write_file contains the filename returned by write_file.
        callback(null, {'file':results.write_file, 'email':'[email protected]'});
    }]
}, function(err, results) {
    console.log('err = ', err);
    console.log('results = ', results);
});


async.auto({
    getData: function(callback){

        setTimeout(function(){
            console.log('got data');
            callback(null, 'mydata');
        }, 300);
    },
    makeFolder: function(callback){
        setTimeout(function() {
            console.log('made folder');
            callback(null, 'myfolder');
        }, 200);
    },
    writeFile:['getData', 'makeFolder', function(results,callback){
        setTimeout(function () {
                console.log('write file');
                callback(null, 'myfile');
        }, 300);
    }],
    emailFiles: ['writeFile', function(results, callback){
        console.log('send email');
        callback(null, results.writeFile);
    }]
},function(err, results){
    console.log(err); //->null
    console.log(results);
    //made folder
    //got data
    //write file
    //send email

    /*
    results{
        makeFolder: 'myfolder',
        getData: 'mydata',
        writeFile: 'myfile',
        emailFiles: 'myfile'
    }
    */
});

nodejs第三方模块async异步流程控制模块

猜你喜欢