的Ajax调用循环 - 访问循环计数器？ [英] loop of ajax calls - accessing loop counter?

问题描述

我在这里卡住了，任何帮助，将AP preciated。

我有一个项目列表框，我想找回在通过AJAX的列表（调用Web服务）上的每一项数据。所检索的数据需要在此基础上排它从叫做被操纵。 如果我通过在该行的参数，它的值总是人比行数越大。 有没有一种方法来传递它的时候了ajax呼叫发起的价值呢？

  VAR = numRows行list.options.length;
    对于（VAR行= 0;行＆LT; numRows行;行++）
    {
      VAR值= list.options [行] .value的;
      VAR xmlHttpObj = CreateXmlHtt prequestObject（）;
      如果（xmlHttpObj！= NULL）
      {
        xmlHttpObj.open（POST，Async.ashx ARG1 = GetPhysicalPathInfo和放大器; ARG2 =+值，真正的）;
        xmlHttpObj.onreadystatechange =函数（行）
        {
          需要知道我们是从什么行// code
        }
      }
      xmlHttpObj.send（）;
    }
 

解决方案

通过自动执行的功能创建一个闭包：

  VAR = numRows行list.options.length;
对于（VAR行= 0;行＆LT; numRows行;行++）
{
  ！函数（行）{
      VAR值= list.options [行] .value的;
      VAR xmlHttpObj = CreateXmlHtt prequestObject（）;
      如果（xmlHttpObj！= NULL）
      {
        xmlHttpObj.open（POST，Async.ashx ARG1 = GetPhysicalPathInfo和放大器; ARG2 =+值，真正的）;
        xmlHttpObj.onreadystatechange =功能（）
        {
          需要知道我们是从什么行// code
        }
      }
      xmlHttpObj.send（）;
  }（行）;
}
 

当然，那就是你发出从环AJAX请求一大红旗。这是非常低效的;考虑做一个电话，从服务器返回一个数组。

I am stuck here, any help would be appreciated.

I have a listbox of items, and I want to retrieve data on each item in the list via AJAX (which calls a webservice). The retrieved data needs to be manipulated based on which row it was called from. If I pass in the row parameter, its value is always one greater than the number of rows. Is there a way to pass in the value it had at the time the ajax call was initiated?

    var NumRows = list.options.length;
    for ( var row = 0; row < NumRows; row ++ )
    {
      var Value = list.options[row].value;
      var xmlHttpObj = CreateXmlHttpRequestObject();
      if ( xmlHttpObj != null )
      {
        xmlHttpObj.open( "POST", "Async.ashx?arg1=GetPhysicalPathInfo&arg2=" + Value, true );
        xmlHttpObj.onreadystatechange = function ( row )
        {
          // code that needs to know what row we were from
        }
      }
      xmlHttpObj.send();
    }

解决方案

Create a closure with a self-executing function:

var NumRows = list.options.length;
for ( var row = 0; row < NumRows; row ++ )
{
  !function(row) {
      var Value = list.options[row].value;
      var xmlHttpObj = CreateXmlHttpRequestObject();
      if ( xmlHttpObj != null )
      {
        xmlHttpObj.open( "POST", "Async.ashx?arg1=GetPhysicalPathInfo&arg2=" + Value, true );
        xmlHttpObj.onreadystatechange = function ()
        {
          // code that needs to know what row we were from
        }
      }
      xmlHttpObj.send();
  }(row);
}

Of course, it's a major red flag that you're issuing AJAX requests from a loop. This is highly inefficient; consider making one call and returning an array from the server.

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