# Async.js
[![Build Status via Travis CI](https://travis-ci.org/caolan/async.svg?branch=master)](https://travis-ci.org/caolan/async)
[![NPM version](http://img.shields.io/npm/v/async.svg)](https://www.npmjs.org/package/async)
[![Coverage Status](https://coveralls.io/repos/caolan/async/badge.svg?branch=master)](https://coveralls.io/r/caolan/async?branch=master)
[![Join the chat at https://gitter.im/caolan/async](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/caolan/async?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
Async is a utility module which provides straight-forward, powerful functions
for working with asynchronous JavaScript. Although originally designed for
use with [Node.js](http://nodejs.org) and installable via `npm install async`,
it can also be used directly in the browser.
Async is also installable via:
- [bower](http://bower.io/): `bower install async`
- [component](https://github.com/component/component): `component install
caolan/async`
- [jam](http://jamjs.org/): `jam install async`
- [spm](http://spmjs.io/): `spm install async`
Async provides around 20 functions that include the usual 'functional'
suspects (`map`, `reduce`, `filter`, `each`…) as well as some common patterns
for asynchronous control flow (`parallel`, `series`, `waterfall`…). All these
functions assume you follow the Node.js convention of providing a single
callback as the last argument of your `async` function.
## Quick Examples
```javascript
async.map(['file1','file2','file3'], fs.stat, function(err, results){
// results is now an array of stats for each file
});
async.filter(['file1','file2','file3'], fs.exists, function(results){
// results now equals an array of the existing files
});
async.parallel([
function(){ ... },
function(){ ... }
], callback);
async.series([
function(){ ... },
function(){ ... }
]);
```
There are many more functions available so take a look at the docs below for a
full list. This module aims to be comprehensive, so if you feel anything is
missing please create a GitHub issue for it.
## Common Pitfalls <sub>[(StackOverflow)](http://stackoverflow.com/questions/tagged/async.js)</sub>
### Synchronous iteration functions
If you get an error like `RangeError: Maximum call stack size exceeded.` or other stack overflow issues when using async, you are likely using a synchronous iterator. By *synchronous* we mean a function that calls its callback on the same tick in the javascript event loop, without doing any I/O or using any timers. Calling many callbacks iteratively will quickly overflow the stack. If you run into this issue, just defer your callback with `async.setImmediate` to start a new call stack on the next tick of the event loop.
This can also arise by accident if you callback early in certain cases:
```js
async.eachSeries(hugeArray, function iterator(item, callback) {
if (inCache(item)) {
callback(null, cache[item]); // if many items are cached, you'll overflow
} else {
doSomeIO(item, callback);
}
}, function done() {
//...
});
```
Just change it to:
```js
async.eachSeries(hugeArray, function iterator(item, callback) {
if (inCache(item)) {
async.setImmediate(function () {
callback(null, cache[item]);
});
} else {
doSomeIO(item, callback);
//...
```
Async guards against synchronous functions in some, but not all, cases. If you are still running into stack overflows, you can defer as suggested above, or wrap functions with [`async.ensureAsync`](#ensureAsync) Functions that are asynchronous by their nature do not have this problem and don't need the extra callback deferral.
If JavaScript's event loop is still a bit nebulous, check out [this article](http://blog.carbonfive.com/2013/10/27/the-javascript-event-loop-explained/) or [this talk](http://2014.jsconf.eu/speakers/philip-roberts-what-the-heck-is-the-event-loop-anyway.html) for more detailed information about how it works.
### Multiple callbacks
Make sure to always `return` when calling a callback early, otherwise you will cause multiple callbacks and unpredictable behavior in many cases.
```js
async.waterfall([
function (callback) {
getSomething(options, function (err, result) {
if (err) {
callback(new Error("failed getting something:" + err.message));
// we should return here
}
// since we did not return, this callback still will be called and
// `processData` will be called twice
callback(null, result);
});
},
processData
], done)
```
It is always good practice to `return callback(err, result)` whenever a callback call is not the last statement of a function.
### Binding a context to an iterator
This section is really about `bind`, not about `async`. If you are wondering how to
make `async` execute your iterators in a given context, or are confused as to why
a method of another library isn't working as an iterator, study this example:
```js
// Here is a simple object with an (unnecessarily roundabout) squaring method
var AsyncSquaringLibrary = {
squareExponent: 2,
square: function(number, callback){
var result = Math.pow(number, this.squareExponent);
setTimeout(function(){
callback(null, result);
}, 200);
}
};
async.map([1, 2, 3], AsyncSquaringLibrary.square, function(err, result){
// result is [NaN, NaN, NaN]
// This fails because the `this.squareExponent` expression in the square
// function is not evaluated in the context of AsyncSquaringLibrary, and is
// therefore undefined.
});
async.map([1, 2, 3], AsyncSquaringLibrary.square.bind(AsyncSquaringLibrary), function(err, result){
// result is [1, 4, 9]
// With the help of bind we can attach a context to the iterator before
// passing it to async. Now the square function will be executed in its
// 'home' AsyncSquaringLibrary context and the value of `this.squareExponent`
// will be as expected.
});
```
## Download
The source is available for download from
[GitHub](https://github.com/caolan/async/blob/master/lib/async.js).
Alternatively, you can install using Node Package Manager (`npm`):
npm install async
As well as using Bower:
bower install async
__Development:__ [async.js](https://github.com/caolan/async/raw/master/lib/async.js) - 29.6kb Uncompressed
## In the Browser
So far it's been tested in IE6, IE7, IE8, FF3.6 and Chrome 5.
Usage:
```html
<script type="text/javascript" src="async.js"></script>
<script type="text/javascript">
async.map(data, asyncProcess, function(err, results){
alert(results);
});
</script>
```
## Documentation
Some functions are also available in the following forms:
* `<name>Series` - the same as `<name>` but runs only a single async operation at a time
* `<name>Limit` - the same as `<name>` but runs a maximum of `limit` async operations at a time
### Collections
* [`each`](#each), `eachSeries`, `eachLimit`
* [`forEachOf`](#forEachOf), `forEachOfSeries`, `forEachOfLimit`
* [`map`](#map), `mapSeries`, `mapLimit`
* [`filter`](#filter), `filterSeries`, `filterLimit`
* [`reject`](#reject), `rejectSeries`, `rejectLimit`
* [`reduce`](#reduce), [`reduceRight`](#reduceRight)
* [`detect`](#detect), `detectSeries`, `detectLimit`
* [`sortBy`](#sortBy)
* [`some`](#some), `someLimit`
* [`every`](#every), `everyLimit`
* [`concat`](#concat), `concatSeries`
### Control Flow
* [`series`](#seriestasks-callback)
* [`parallel`](#parallel), `parallelLimit`
* [`whilst`](#whilst), [`doWhilst`](#doWhilst)
* [`until`](#until), [`doUntil`](#doUntil)
* [`during`](#during), [`doDuring`](#doDuring)
* [`forever`](#forever)
* [`waterfall`](#waterfall)
* [`compose`](#compose)
* [`seq`](#seq)
* [`applyEach`](#applyEach), `applyEachSeries`
* [`queue`](#queue), [`priorityQueue`](#priorityQueue)
* [`cargo`](#cargo)
* [`auto`](#auto)
* [`retry`](#retry)
* [`iterator`](#iterator)
* [`times`](#times), `timesSeri
没有合适的资源?快使用搜索试试~ 我知道了~
nwjs客户端更新模块
共665个文件
js:231个
json:128个
md:97个
需积分: 50 7 下载量 115 浏览量
2019-08-11
02:30:09
上传
评论 1
收藏 1.19MB ZIP 举报
温馨提示
nw.js 客户端更新模块
资源推荐
资源详情
资源评论
收起资源包目录
nwjs客户端更新模块 (665个子文件)
almond.0 2KB
sshpk-conv.1 4KB
sshpk-sign.1 2KB
sshpk-verify.1 2KB
almond.1 558B
address 673B
AUTHORS 217B
AUTHORS 217B
range.bnf 629B
benchmark-native.c 613B
calendar 945B
card 2KB
har-validator.cmd 204B
sshpk-verify.cmd 186B
sshpk-sign.cmd 182B
sshpk-conv.cmd 182B
uuid.cmd 178B
semver.cmd 176B
jsl.node.conf 7KB
jsl.node.conf 7KB
Makefile.deps 1KB
.dockerignore 71B
.editorconfig 166B
.dir-locals.el 178B
.eslintignore 15B
.eslintignore 5B
.eslintrc 5KB
.eslintrc 2KB
.eslintrc 1KB
.eslintrc 477B
geo 166B
.gitignore 53B
.gitmodules 205B
.gitmodules 0B
bench.gnu 6KB
har-validator 2KB
har-validator 333B
test.html 340B
example.html 200B
hyper-schema 1KB
hyper-schema 1KB
hyper-schema 1KB
hyper-schema 942B
hyper-schema 936B
dashdash.bash_completion.in 14KB
interfaces 845B
pubsuffix.js 146KB
index.js 66KB
nacl-fast.js 62KB
deflater.js 60KB
browser.js 58KB
server.js 49KB
index.js 41KB
request.js 39KB
async.js 38KB
async.js 38KB
cookie.js 37KB
dashdash.js 34KB
nacl.js 33KB
nacl-fast.min.js 32KB
semver.js 32KB
uri.js 28KB
browser.js 26KB
_stream_readable.js 25KB
index.js 24KB
index.js 24KB
core.js 20KB
nacl.min.js 19KB
server.js 18KB
index.js 17KB
parse.js 17KB
adm-zip.js 17KB
eddsa.js 17KB
client.js 16KB
index.js 16KB
test.js 15KB
ec.js 15KB
qs.js 15KB
inflater.js 15KB
_stream_writable.js 14KB
index.js 14KB
signer.js 13KB
index.js 13KB
async.min.js 12KB
stringify.js 12KB
pkcs8.js 12KB
jsprim.js 11KB
form_data.js 11KB
zipFile.js 11KB
is-property.js 11KB
zipEntry.js 11KB
client.js 10KB
misc.js 10KB
validate.js 10KB
client.js 10KB
entryHeader.js 10KB
aws4.js 10KB
parser.js 10KB
index.js 10KB
writer.test.js 9KB
共 665 条
- 1
- 2
- 3
- 4
- 5
- 6
- 7
资源评论
weixin_39841882
- 粉丝: 443
- 资源: 1万+
上传资源 快速赚钱
- 我的内容管理 展开
- 我的资源 快来上传第一个资源
- 我的收益 登录查看自己的收益
- 我的积分 登录查看自己的积分
- 我的C币 登录后查看C币余额
- 我的收藏
- 我的下载
- 下载帮助
最新资源
- 卡方数据.sav
- Python实现基于Django框架的二手物品购物网站设计源码+数据库.zip
- 基于Python和Django的二手物品购物网站设计源码+数据库脚本.zip
- 【计算机毕业设计】基于h5的移动网赚项目小程序【源码+lw+部署文档+讲解】
- 【计算机毕业设计】基于ssm-vue的oa系统设计与实现【源码+lw+部署文档+讲解】
- 基于pytorch实现的YOLOV5+SORT的车辆行人目标识别及追踪系统源码.zip
- 【计算机毕业设计】基于servlet+jdbc的在线选房系统设计与实现【源码+lw+部署文档+讲解】
- 投身科技创新,勇担时代先锋.pptx
- 【计算机毕业设计】基于SSM的仿微博系统的设计与实现【源码+lw+部署文档+讲解】
- 使用 Web Components 实现,遵循 Material You 设计规范的 Web 前端组件库
资源上传下载、课程学习等过程中有任何疑问或建议,欢迎提出宝贵意见哦~我们会及时处理!
点击此处反馈
安全验证
文档复制为VIP权益,开通VIP直接复制
信息提交成功