JavaScript error is not a function

Question

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   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      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      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   amp  amp              win parent    null   amp  amp              win parent    win                  increment the number of findAPITries       findAPITries              Note  7 is an arbitrary number  but should be more than sufficient       if  findAPITries  gt  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   amp  amp           window opener    null   amp  amp           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      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   What am I missing

User · Answer

I also hit this error  In my case the root cause was async related  during a codebase refactor    An asynchronous function that builds the object to which the  not a function  function   belongs was not awaited  and the subsequent attempt to invoke the function throws the error  example below   const car   carFactory getCar    car drive     throws TypeError  drive is not a function   The fix was   const car   await carFactory getCar    car drive     Posting this incase it helps anyone else facing this error

User · Answer

I received this error when I copied a class object using JSON parse and JSON stringify   which removed the function like  class Rectangle     constructor height  width        this height   height      this width   width           Method   calcArea         return this height   this width         const square   new Rectangle 10  10    console log  area of square     square calcArea      const squareCopy   JSON parse JSON stringify square        Will throw an exception since calcArea   is no longer function  console log  area of square copy     squareCopy calcArea

User · Answer

Your LMSInitialize function is declared inside Scorm API 12 function  So it can be seen only in Scorm API 12 function s scope   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

User · Answer

For more generic advice on debugging this kind of problem MDN have a good article TypeError   x  is not a function      It was attempted to call a value like a function  but the value is not   actually a function  Some code expects you to provide a function  but   that didn t happen       Maybe there is a typo in the function name  Maybe the object you are   calling the method on does not have this function  For example    JavaScript objects have no map function  but JavaScript Array object   do    Basically the object  all functions in js are also objects  does not exist where you think it does  This could be for numerous reasons including not an extensive list     Missing script library Typo The function is within a scope that you currently do not have access to  e g      x000D   x000D  var x   function    x000D     var y   function     x000D        alert  fired y    x000D       x000D     x000D       x000D    the global scope can t access y because it is closed over in x and not exposed x000D    y is not a function err triggered x000D  x y    x000D   x000D   x000D     Your object function does not have the function your calling     x000D   x000D  var x   function    x000D     var y   function     x000D        alert  fired y    x000D       x000D     x000D       x000D    z is not a function error  as above  triggered x000D  x z    x000D   x000D   x000D

[javascript] JavaScript error: "is not a function"

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