-
Notifications
You must be signed in to change notification settings - Fork 1
async.js学习记录
林航 edited this page Jan 1, 2018
·
1 revision
[toc]
1. 多个异步依次顺序执行。如果有异常抛出时就立即执行回调函数, 回调函数的err为抛出的异常;如果没有异常抛出,当所有异步函数完成后,执行成功回调函数,err值为null, result 为异步数组的结果数组
async.series([
function(callback) {
doAsync1(arg, callback);
},
function(callback) {
doAsync2(arg, callback);
},
function(callback) {
doAsync3(arg, callback);
}
], function(err, result) {
console.log(result);
});
在线demo: http://jsbin.com/sisasu/edit?js,console,output
2.多个异步依次顺序执行,且后面异步函数的依赖前面异步函数的输出
async.waterfall([
function(callback) {
doAsync1(2, callback);
},
function(arg, callback) {
doAsync2(arg, callback);
},
function(arg, callback) {
doAsync3(arg, callback);
}
], function(err, result) {
console.log(result);
});
在线demo: http://jsbin.com/yozuje/edit?js,console,output
3.多个异步并行执行,当所有异步函数执行完成后执行回调函数,回到函数的参数为之前异步函数执行结果的数组,如果需要限制并行执行的数量可以使用parallelLimit
async.parallel([
function(callback) {
doAsync1(arg, callback);
},
function(callback) {
doAsync2(arg, callback);
},
function(callback) {
doAsync3(arg, callback);
}
], function(err, result) {
console.log(result);
});
在线demo: http://jsbin.com/mugixu/edit?js,console,output
async.each(arr, doAsync, function(err, result){
console.log(result);
});
// 等同于
async.each(arr, function(item, callback){
doAsync(item, callback);
}, function(err, result){
console.log(result);
});
在线demo: http://jsbin.com/supuko/edit?js,console,output
var fs = require('fs');
var mysql = require('mysql');
var async = require('async');
var connection = mysql.createConnection({
host: 'localhost',
user: 'root',
password: 'root',
database: 'rest'
});
connection.connect();
var ruleid = [277, 276, 278];
function exportData(num, cb) {
async.waterfall([
function(callback) {
connection.query('SELECT * from user where name = ?', num, callback);
},
function(rows, fields, callback) {
var result = [];
rows.forEach(function(item) {
result.push(data.name);
result.push(arr.join("\t") + "\n");
});
var out = result.join('');
fs.writeFile(num + '.txt', out, callback);
}
], function(err, result) {
console.log(num, 'is saved');
cb(err, num);
});
};
async.each(ruleid, function(item, callback) {
exportData(item, callback);
}, function done() {
console.log('ok');
connection.end();
});