使用非同步

該非同步包提供功能非同步程式碼。

使用 auto 函式可以定義兩個或多個函式之間的非同步關係：

var async = require('async');

async.auto({
    get_data: function(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':'user@example.com'});
    }]
}, function(err, results) {
    console.log('err = ', err);
    console.log('results = ', results);
});

這個程式碼可以通過以正確的順序呼叫 get_data，make_folder，write_file 和 email_link 來同步進行。Async 會為你跟蹤結果，如果發生錯誤（callback 的第一個引數不等於 null），它將停止執行其他功能。