# async.js * 仓库 [https://github.com/caolan/async](https://github.com/caolan/async) * 文档 [http://caolan.github.io/async/](http://caolan.github.io/async/) 比如each方法，依次完成 ~~~ async.each(openFiles, saveFile, function(err){ // if any of the saves produced an error, err would equal that error }); ~~~ 比如瀑布式的 ~~~ async.waterfall([ function(callback) { callback(null, 'one', 'two'); }, function(arg1, arg2, callback) { // arg1 now equals 'one' and arg2 now equals 'two' callback(null, 'three'); }, function(arg1, callback) { // arg1 now equals 'three' callback(null, 'done'); } ], function (err, result) { // result now equals 'done' }); // Or, with named functions: async.waterfall([ myFirstFunction, mySecondFunction, myLastFunction, ], function (err, result) { // result now equals 'done' }); function myFirstFunction(callback) { callback(null, 'one', 'two'); } function mySecondFunction(arg1, arg2, callback) { // arg1 now equals 'one' and arg2 now equals 'two' callback(null, 'three'); } function myLastFunction(arg1, callback) { // arg1 now equals 'three' callback(null, 'done'); } ~~~ 比如对各种api或数据结构的扩展。 总之async.js是个不错的库，但比过于独立，和promise/a+规范不一样，也就是说我们需要多学aysnc.js，又不能和promise/a+一起用 所以，不如直接上promise/a+。