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+。