javascript - 如何在 JavaScript 或 Node 中使其异步？

Question

var responseArr = new Array();
async.each(response, function (value, k) {
    if(isDateFlag)
    {
         var defaultValue = value.auction_id;
         grpArray.push(value.title);
         var postData = {
             parent_id : parent_id,
             defaultValue : defaultValue,
             isDateFlag : isDateFlag,
             search_text : search_text
         }
         getChildNotificationList(postData, function (childArrayData) {
            //Creating the response array

             responseArr.push({
                'notification_id' : childArrayData['notification_id'], 
                'notification_text' : childArrayData['notification_text']
             });
        });

     }
});

return responseArr;//Blank Array

我想在从子数据查询中操作它之后返回最终的responseArr。它返回空白数组，因为它不等待查询响应。

那么它是如何异步的呢？谢谢

Answer 1

我提到了http://justinklemm.com/node-js-async-tutorial/和 https://github.com/caolan/async .

发生这种情况是因为控件继续执行代码，因为 javascript 是同步的。为了获得预期的结果，修改代码如下:

var responseArr = new Array();
async.each(response, function (value, k) {
  if(isDateFlag){
    var defaultValue = value.auction_id;
    grpArray.push(value.title);
    var postData = {
      parent_id : parent_id,
      defaultValue : defaultValue,
      isDateFlag : isDateFlag,
      search_text : search_text
    }
    getChildNotificationList(postData, function (childArrayData) {
      //Creating the response array

      responseArr.push({
        'notification_id' : childArrayData['notification_id'], 
        'notification_text' : childArrayData['notification_text']
      });
      k();
    });
  } else {
    k();
  }
}, function (err) {
  if (err) {
    console.log(err);
  } else {
    return responseArr;
  }
});

以上代码位于功能 block 内。调用该函数即可得到结果。

使用 async.map 包含答案:

async.map(response, function (value, k) {
  if(isDateFlag){
    var defaultValue = value.auction_id;
    grpArray.push(value.title);
    var postData = {
      parent_id : parent_id,
      defaultValue : defaultValue,
      isDateFlag : isDateFlag,
      search_text : search_text
    }
    getChildNotificationList(postData, function (childArrayData) {

      k(null, {
        'notification_id' : childArrayData['notification_id'], 
        'notification_text' : childArrayData['notification_text']
      });
    });
  } else {
    k(null, {
      'notification_id' : '', 
      'notification_text' : ''
    });
  }
}, function(err, results){
  // results is now an array
  return results;
});