JavaScript错误：“不是函数” [英] JavaScript error: "is not a function"

问题描述

看起来$ smth不是函数是一个非常常见的JavaScript问题，但在查看了很多线程后，我仍然无法理解在我的情况下导致它的原因。

It looks like "$smth is not a function" is a very common problem with JavaScript, yet after looking through quite a few threads I still cannot understand what is causing it in my case.

我有一个自定义对象，定义为：

I have a custom object, defined as:

function Scorm_API_12() {
var Initialized = false;

function LMSInitialize(param) {
    errorCode = "0";
    if (param == "") {
        if (!Initialized) {
            Initialized = true;
            errorCode = "0";
            return "true";
        } else {
            errorCode = "101";
        }
    } else {
        errorCode = "201";
    }
    return "false";
}

// some more functions, omitted.
}

var API = new Scorm_API_12();

然后在另一个脚本中，我尝试以下列方式使用此API：

Then in a different script I am trying to use this API in the following way:

var API = null;

function ScormProcessInitialize(){
    var result;

    API = getAPI();

    if (API == null){
        alert("ERROR - Could not establish a connection with the API.");
        return;
    }

    // and here the dreaded error pops up
    result = API.LMSInitialize("");

    // more code, omitted
    initialized = true;
}

getAPI（）内容如下所示：

The getAPI() stuff, looks like this:

var findAPITries = 0;

function findAPI(win)
{
   // Check to see if the window (win) contains the API
   // if the window (win) does not contain the API and
   // the window (win) has a parent window and the parent window
   // is not the same as the window (win)
   while ( (win.API == null) &&
           (win.parent != null) &&
           (win.parent != win) )
   {
      // increment the number of findAPITries
      findAPITries++;

      // Note: 7 is an arbitrary number, but should be more than sufficient
      if (findAPITries > 7)
      {
         alert("Error finding API -- too deeply nested.");
         return null;
      }

      // set the variable that represents the window being
      // being searched to be the parent of the current window
      // then search for the API again
      win = win.parent;
   }
   return win.API;
}

function getAPI()
{
   // start by looking for the API in the current window
   var theAPI = findAPI(window);

   // if the API is null (could not be found in the current window)
   // and the current window has an opener window
   if ( (theAPI == null) &&
        (window.opener != null) &&
        (typeof(window.opener) != "undefined") )
   {
      // try to find the API in the current window�s opener
      theAPI = findAPI(window.opener);
   }
   // if the API has not been found
   if (theAPI == null)
   {
      // Alert the user that the API Adapter could not be found
      alert("Unable to find an API adapter");
   }
   return theAPI;
}

现在，API 可能找到，因为我没有得到无法找到...消息，代码继续尝试初始化它。但是firebug告诉我 API.LMSInitialize不是函数，如果我尝试用 alert（Object.getOwnPropertyNames（API））调试它; ，它给了我一个空白警告。

Now, the API is probably found, because I do not get the "Unable to find..." message, the code proceeds to try to initialize it. But firebug tells me API.LMSInitialize is not a function, and if I try to debug it with alert(Object.getOwnPropertyNames(API));, it gives me a blank alert.

我缺少什么？

推荐答案

您的 LMSInitialize 函数在 Scorm_API_12 函数内声明。所以它只能在 Scorm_API_12 函数的范围内看到。

Your LMSInitialize function is declared inside Scorm_API_12 function. So it can be seen only in Scorm_API_12 function's scope.

如果你想使用像<$ c这样的函数$ c> API.LMSInitialize（），声明 Scorm_API_12 这样的函数：

If you want to use this function like API.LMSInitialize(""), declare Scorm_API_12 function like this:

function Scorm_API_12() {
var Initialized = false;

this.LMSInitialize = function(param) {
    errorCode = "0";
    if (param == "") {
        if (!Initialized) {
            Initialized = true;
            errorCode = "0";
            return "true";
        } else {
            errorCode = "101";
        }
    } else {
        errorCode = "201";
    }
    return "false";
}

// some more functions, omitted.
}

var API = new Scorm_API_12();

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