javascript - async each 中的异步任务 : Callback to be run after all task and sub tasks completed

Question

为此，我正在使用 async.js。我基本上迭代所有数组并使用 aysnc.each 运行删除。

var async = require("async");
var fs = require('fs');


var files = ['a.log', 'b.log', 'c.log'];


async.each(files, function(file, cb) {
  if(file == 'a.log') {
    console.log('its A');
    fs.unlink(file, function(err) {  //delete the particular file
      if(err) {
        console.error(err);
      }
      console.log(file + ' has been Deleted');
    });
  }

  if(file == 'b.log') {
    console.log('its B');
    fs.unlink(file, function(err) {
      if(err) {
        console.error(err);
      }
      console.log(file + ' has been Deleted');
    });
  }

  if(file == 'c.log') {
    console.log('its C');
    fs.unlink(file, function(err) {
      if(err) {
        console.error(err);
      }
      console.log(file + ' has been Deleted');
    });
  }
  cb();
}, function(err) {
  console.log('all done');
});

我现在的输出..删除稍后完成。

its A
its B
its C
all done
a.log has been Deleted
b.log has been Deleted
c.log has been Deleted

我想要实现的是输出类似于下面的内容，其中回调仅在所有每个子任务(删除文件)完成后运行。

its A
its B
its C
a.log has been Deleted
b.log has been Deleted
c.log has been Deleted
all done  //would like this

Answer 1

您的迭代对象的回调被调用得太早(它没有等待 fs.unlink 完成)。
您需要在 fs.unlink 回调中移动对它的调用:

async.each(files, function(file, cb) {
  if(file == 'a.log') {
    ...
  } else if(file == 'b.log') {
    ...
  } else if(file == 'c.log') {
    ...
  }
  ...
  fs.unlink(file, function(err) {
    ...
    cb();
    ...
  }
  ...
}, function(err) {
  console.log('all done');
});