# Async.js
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), it can also be used directly in the
browser. Also supports [component](https://github.com/component/component).
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
### 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](http://github.com/caolan/async).
Alternatively, you can install using Node Package Manager (npm):
npm 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
### Collections
* [each](#each)
* [map](#map)
* [filter](#filter)
* [reject](#reject)
* [reduce](#reduce)
* [detect](#detect)
* [sortBy](#sortBy)
* [some](#some)
* [every](#every)
* [concat](#concat)
### Control Flow
* [series](#series)
* [parallel](#parallel)
* [whilst](#whilst)
* [doWhilst](#doWhilst)
* [until](#until)
* [doUntil](#doUntil)
* [forever](#forever)
* [waterfall](#waterfall)
* [compose](#compose)
* [applyEach](#applyEach)
* [queue](#queue)
* [cargo](#cargo)
* [auto](#auto)
* [iterator](#iterator)
* [apply](#apply)
* [nextTick](#nextTick)
* [times](#times)
* [timesSeries](#timesSeries)
### Utils
* [memoize](#memoize)
* [unmemoize](#unmemoize)
* [log](#log)
* [dir](#dir)
* [noConflict](#noConflict)
## Collections
<a name="forEach" />
<a name="each" />
### each(arr, iterator, callback)
Applies an iterator function to each item in an array, in parallel.
The iterator is called with an item from the list and a callback for when it
has finished. If the iterator passes an error to this callback, the main
callback for the each function is immediately called with the error.
Note, that since this function applies the iterator to each item in parallel
there is no guarantee that the iterator functions will complete in order.
__Arguments__
* arr - An array to iterate over.
* iterator(item, callback) - A function to apply to each item in the array.
The iterator is passed a callback(err) which must be called once it has
completed. If no error has occured, the callback should be run without
arguments or with an explicit null argument.
* callback(err) - A callback which is called after all the iterator functions
have finished, or an error has occurred.
__Example__
```js
// assuming openFiles is an array of file names and saveFile is a function
// to save the modified contents of that file:
async.each(openFiles, saveFile, function(err){
// if any of the saves produced an error, err would equal that error
});
```
---------------------------------------
<a name="forEachSeries" />
<a name="eachSeries" />
### eachSeries(arr, iterator, callback)
The same as each only the iterator is applied to each item in the array in
series. The next iterator is only called once the current one has completed
processing. This means the iterator functions will complete in order.
---------------------------------------
<a name="forEachLimit" />
<a name="eachLimit" />
### eachLimit(arr, limit, iterator, callback)
The same as each only no more than "limit" iterators will be simultaneously
running at any time.
Note that the items are not processed in batches, so there is no guarantee that
the first "limit" iterator functions will complete before any others are
started.
__Arguments__
* arr - An array to iterate over.
* limit - The maximum number of iterators to run at any time.
* iterator(item, callback) - A function to apply to each item in the array.
The iterator is passed a callback(err) which must be called once it has
completed. If no error has occured, the callback should be run without
arguments or with an explicit null argument.
* callback(err) - A callback which is called after all the iterator functions
have finished, or an error has occurred.
__Example__
```js
// Assume documents is an array of JSON objects and requestApi is a
// function that interacts with a rate-limited REST api.
async.eachLimit(documents, 20, requestApi, function(err){
// if any of the saves produced an error, err would equal that error
});
```
---------------------------------------
<a name="map" />
### map(arr, iterator, callback)
Produces a new array of values by mapping each value in the given array through
the iterator function. The iterator is called with an item from the array and a
callback for when it has finished processing. The callback takes 2 arguments,
an error and the transformed item from the array. If the iterator passes an
error to this callback, the main callback for the map function is immediately
called with the error.
Note, that since this function applies the iterator to each item in parallel
there is no guarantee that the iterator functions will complete in order, however
the results array will be in the same order as the original array.
__Arguments__
* arr - An array to iterate over.
* iterator(item, callback) - A function to apply to each item in the array.
The iterator is passed a callback(err, transformed) which must be called once
it has completed with an error (which can be null) and a transformed item.
* callback(err, results) - A callback which is called after all the iterator
functions have finished, or an error has occurred. Results is an array of the
transformed items from the original array.
__Example__
```js
async.map(['file1','file2','file3'], fs.stat, functi
没有合适的资源?快使用搜索试试~ 我知道了~
node-v0.10.16-darwin-x64.tar.gz
1.该资源内容由用户上传,如若侵权请联系客服进行举报
2.虚拟产品一经售出概不退款(资源遇到问题,请及时私信上传者)
2.虚拟产品一经售出概不退款(资源遇到问题,请及时私信上传者)
版权申诉
0 下载量 2 浏览量
2024-05-17
23:12:21
上传
评论
收藏 4.3MB GZ 举报
温馨提示
共1083个文件
js:350个
md:176个
html:107个
node-v0.10.16-darwin-x64.tar
资源推荐
资源详情
资源评论
收起资源包目录
node-v0.10.16-darwin-x64.tar.gz (1083个子文件)
node.1 19KB
npm-install.1 9KB
npm-README.1 8KB
npm-shrinkwrap.1 7KB
npm.1 5KB
npm-view.1 3KB
npm-cache.1 2KB
npm-link.1 2KB
npm-ls.1 2KB
npm-version.1 2KB
npm-dedupe.1 2KB
npm-config.1 2KB
npm-help.1 1KB
npm-explore.1 1KB
npm-edit.1 1KB
npm-owner.1 1KB
npm-submodule.1 1KB
npm-bugs.1 1KB
npm-docs.1 1KB
npm-help-search.1 1KB
npm-adduser.1 1KB
npm-unpublish.1 969B
npm-completion.1 957B
npm-deprecate.1 929B
npm-pack.1 923B
npm-init.1 885B
npm-publish.1 878B
npm-update.1 803B
repo.1 750B
npm-search.1 724B
npm-star.1 663B
npm-restart.1 652B
npm-stars.1 647B
npm-build.1 644B
npm-prune.1 621B
npm-run-script.1 621B
npm-rebuild.1 597B
npm-test.1 562B
npm-tag.1 551B
npm-rm.1 548B
npm-uninstall.1 548B
npm-outdated.1 505B
npm-root.1 499B
npm-bundle.1 498B
npm-bin.1 493B
npm-start.1 478B
npm-stop.1 474B
npm-prefix.1 472B
npm-whoami.1 438B
npm.3 4KB
npm-view.3 4KB
npm-ls.3 2KB
npm-search.3 1KB
npm-config.3 1KB
npm-owner.3 1KB
npm-link.3 1KB
npm-init.3 1KB
npm-help-search.3 1KB
npm-submodule.3 1KB
npm-deprecate.3 1KB
npm-run-script.3 1024B
npm-publish.3 993B
npm-edit.3 970B
npm-tag.3 969B
npm-load.3 850B
npm-shrinkwrap.3 802B
npm-explore.3 801B
npm-commands.3 793B
npm-pack.3 748B
npm-install.3 746B
npm-unpublish.3 736B
npm-version.3 715B
npm-docs.3 714B
repo.3 713B
npm-bugs.3 712B
npm-restart.3 695B
npm-uninstall.3 623B
npm-rebuild.3 580B
npm-prune.3 562B
npm-test.3 508B
npm-root.3 480B
npm-update.3 478B
npm-whoami.3 477B
npm-prefix.3 453B
npm-outdated.3 449B
npm-start.3 425B
npm-stop.3 419B
npm-bin.3 407B
ctio.3ctype 8KB
package.json.5 20KB
npm-json.5 20KB
npm-folders.5 8KB
npm-global.5 8KB
npmrc.5 2KB
npm-config.7 23KB
npm-faq.7 14KB
npm-scripts.7 10KB
npm-developers.7 7KB
npm-index.7 6KB
npm-coding-style.7 6KB
共 1083 条
- 1
- 2
- 3
- 4
- 5
- 6
- 11
资源评论
程序员Chino的日记
- 粉丝: 3028
- 资源: 4万+
下载权益
C知道特权
VIP文章
课程特权
开通VIP
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
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