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javascript - JavaScript 中长时间运行的任务

转载 作者：行者123 更新时间：2023-12-03 12:41:32 25 4
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我有以下用于 JavaScript 中长时间运行命令的代码。这有点类似于this thread 。但是我修改了代码以满足我的要求，但现在它似乎不起作用。有人可以建议如何在后台运行此命令时显示“正在处理请求，请等待..”类型的消息:

<html>
<head>
<title>JavaScript Remote Exec Test</title>
<script type="text/javascript">
    function defer(func) {
        var proc = function(){
            func();
        }
    setTimeout(proc, 50);
    }

    function GetPC()
    {
        var strComputerName = "NA";
        var outObj = document.getElementById("outputText");

        try 
        {
            var getPCNameCommand = new ActiveXObject("WScript.Shell");
            var cmdPCName = getPCNameCommand.Exec("c:\\windows\\system32\\cmd.exe /c hostname");

            strComputerName = cmdPCName.StdOut.ReadAll();
        }
        catch (ex)
        {
            strComputerName = "Can't retrive PC name: " + ex;
        }

        return strComputerName; 
    }

    function LaunchApp()
    {
        var appPath = "c:\\windows\\system32\\Gpupdate.exe";
        var errormessage = appPath;
        var strResult = "";
        var strComputerName = GetPC();
        var outObj = document.getElementById("outputText");
        outObj.innerHTML = "Status: Updating group policy for " + strComputerName + "...";

        defer(UpdateGPO);
/*      try
        {
            var gpuExec = new ActiveXObject("WScript.Shell");
            var execResult = gpuExec.Exec(appPath);

            while (execResult.Status == 0) // wait for the command to finish
            {
                outObj.innerHTML = "Updating group policy. \n\n For Computer:\t" + strComputerName;
            }

            strResult = execResult.StdOut.ReadAll();
            strResult = strResult.replace(".","\n");
            outObj.innerHTML = strResult;
        }
        catch (ex)
        {
            errMsg = errormessage + " could not be launched. \n\n" + ex;
            outObj.innerHTML = errMsg;
        }   
*/
    }
    function UpdateGPO() {
    try
        {
            var gpuExec = new ActiveXObject("WScript.Shell");
            var execResult = gpuExec.Exec(appPath);

            while (execResult.Status == 0) // wait for the command to finish
            {
                //outObj.innerHTML = "Updating group policy. \n\n For Computer:\t" + strComputerName + ". Please wait...";
                sleep(5);
            }

            strResult = execResult.StdOut.ReadAll();
            strResult = strResult.replace(".","\n");
            outObj.innerHTML = strResult;
        }
    catch (ex)
        {
            errMsg = errormessage + " could not be launched. \n\n" + ex;
            outObj.innerHTML = errMsg;
        }   
    }
</script>
</head>
<body style="font-family:'Segoe UI';">
<input type="button" value="Update Group Policy" onclick="LaunchApp();"></input>
<p id="outputText">Waiting for command</p>
</body>
</html>

最佳答案

好的，让我看看是否可以解释一下这里的问题是什么......

        while (execResult.Status == 0) // wait for the command to finish
        {
            outObj.innerHTML = "Updating group policy. \n\n For Computer:\t" + strComputerName;
        }

JavaScript 是单线程，这意味着它一次只能做一件事。 (目前，这是忽略网络 worker ，这不计入这个答案。)

所以..你正在做一个while循环，但你永远不会给浏览器“呼吸”的机会并更新execResult.Status，所以你真正拥有的是一个无限循环。

那里没有足够的代码让我重现问题，因此您必须处理解决方案的“猜测”:

function waitForComplete() {
  // execResult is in scope...
  if (execResult.Status == 0) // wait for the command to finish
  {
    outObj.innerHTML = "Updating group policy. \n\n For Computer:\t" + strComputerName;
  } else {
    window.setTimeout(waitForComplete, 250);
  }
}


var gpuExec = new ActiveXObject("WScript.Shell");
var execResult = gpuExec.Exec(appPath);
waitForComplete();

关于javascript - JavaScript 中长时间运行的任务，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23510902/

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