Nodejs发送瀑布请求

Question

我有带文件夹名称的动态数组，并使用 zipFolder 创建了一个 zip 由于库是异步的，我遇到了问题，即

zipFolder(source,dest,callback)

因为它是异步调用，所以需要时间，我想阻止下一个请求，除非第一个响应为真，

function (req, res)
     var folder = ['N','PP','Y'];//dynamic just an example

        for( var i = 0 ; i < folder.length ; i++) {
            var source = path.join(basePath,'/download/'+folder[i]);
            var dest =   path.join(basePath,'/createZip/'+folder[i]+'.zip');
            console.log('sending',folders[i])


            //this is async
            zipFolder(source,dest, function(err) {
                if(err) {
                    console.log('oh no!', err);
                } else {
                    console.log('EXCELLENT');//want to send the second,third,fourth if success
                }
            });
        }

总结：输出应该是这样的：

发送文件 1 if success/response 发送文件 2 if success/response

想要瀑布之类的东西等待回调响应发送第二个文件

另外我想要一个方法来知道完成回调所以我可以发回响应

Answer 1

尝试使用异步 waterfall 方法

https://caolan.github.io/async/docs.html#waterfall

Runs the tasks array of functions in series, each passing their results to the next in the array. However, if any of the tasks pass an error to their own callback, the next function is not executed, and the main callback is immediately called with the error

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'
});

更新

在你的用例中 eachSeries 更适用。

 var folder = ['N','PP','Y'];


      async.eachSeries(folder, function(item,callback){
            var source = path.join(basePath,'/download/'+item);
            var dest =   path.join(basePath,'/createZip/'+item+'.zip');

            zipFolder(source,dest, function(err) {
                if(err) {
                    console.log('oh no!', err);
                    callback();
                } else {
                    console.log('EXCELLENT');//want to send the second,third,fourth if success
                    callback();
                }
            });

     },function(){
         console.log('all items uploaded');
    });    .

Answer 2

你可以像这样使用每一个：

var each = require('async-each-series')
      var folder = ['N','PP','Y'];


       each(folder, function(items,callback){
        //insert each items to db in async way
           var source = path.join(basePath,'/download/'+items);
           var dest =   path.join(basePath,'/createZip/'+items+'.zip');
           zipFolder(source,dest, function(err) {
                    if(err) {
                        console.log('oh no!', err);
                    } else {
                        console.log(items,'inserted')
                        callback()
                    }
                });

    },function(err){
           if(err) console.log('error occured')
        console.log('all items uploaded');
    });

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