Possible cases for Javascript error Expected identifier string or number

Question

Some users are reporting occasional JS errors on my site  The error message says  Expected identifier  string or number  and the line number is 423725915  which is just an arbitrary number and changes for each report when this occurs   This mostly happens with IE7  Mozilla 4 0 browsers   I scanned my code a bunch of times and ran jslint but it didn t pick anything up - anyone know of the general type of JS problems that lead to this error message

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This sounds to me like a script that was pulled in with src  and loaded just halfway  causing a syntax error sine the remainder is not loaded

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The cause of this type of error can often be a misplaced comma in an object or array definition   var obj        id  23     name   test     lt --     If it appears at a random line  maybe it s part of an object defintion you are creating dynamically

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IE7 has problems with arrays of objects  columns        field   id     header   ID         field   name     header   Name       this comma was the problem

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Actually I got something like that on IE recently and it was related to JavaScript syntax  errors   I say error in quotes because it was fine everywhere but on IE  This was under IE6  The problem was related to JSON object creation and an extra comma  such as    one 1  two 2  three 3      IE6 really doesn t like that comma after 3  You might look for something like that  touchy little syntax formality issues   Yeah  I thought the multi-million line number in my 25 line JavaScript was interesting too   Good luck

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This can also happen in Typescript if you call a function in middle of nowhere inside a class  For example  class Dojo implements Sensei        console log  Hi       ERROR Identifier expected       constructor         Function calls  like console log   must be inside functions  Not in the area where you should be declaring class fields

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Using the word class as a key in a Javascript dictionary can also trigger the dreaded  Expected identifier  string or number  error because class is a reserved keyword in Internet Explorer   BAD    class    overlay      ERROR  Expected identifier  string or number   GOOD    class    overlay     When using a reserved keyword as a key in a Javascript dictionary  enclose the key in quotes   Hope this hint saves you a day of debugging hell

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Just saw the bug in one of my applications  as a catch-all  remember to enclose the name of all javascript properties that are the same as keyword   Found this bug after attending to a bug where an object such as   var x     class   myClass   function   myFunction      generated the error  class and function are keywords  this was fixed by adding quotes  var x      class    myClass    function    myFunction      I hope to save you some time

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As noted previously  having an extra comma threw an error   Also in IE 7 0  not having a semicolon at the end of a line caused an error  It works fine in Safari and Chrome  with no errors in console

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Remove the unwanted   sign in the function  you will get the solution   Refer this  http   blog favrik com 2007 11 29 ie7-error-expected-identifier-string-or-number

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You may hit this problem while using Knockout JS  If you try setting class attribute like the example below it will fail    lt span data-bind  attr    class  something      gt  lt  span gt    Escape the class string like this    lt span data-bind  attr     class   something      gt  lt  span gt    My 2 cents

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http   closure-compiler appspot com home will pick this error up with an accurate reference to the actual line number in the offending script

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Here is a easy technique to debug the problem  echo out the script code to the console  Copy the code from the console into your IDE  Most IDE s perform error checking on the code and highlight errors  You should be able to see the error almost immediately in your JavaScript HTML editor

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IE7 is much less forgiving than newer browsers  especially Chrome   I like to use JSLint to find these bugs   It will find these improperly placed commas  among other things   You will probably want to activate the option to ignore improper whitespace   In addition to improperly placed commas  at this blog in the comments someone reported      I ve been hunting down an error that only said  Expected identifier    only in IE  7   My research led me to this page  After some   frustration  it turned out that the problem that I used a reserved   word as a function name   switch    THe error wasn t clear and it   pointed to the wrong line number

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Another variation of this bug  I had a function named  continue  and since it s a reserved word it threw this error  I had to rename my function  continueClick

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This is a definitive un-answer  eliminating a tempting-but-wrong answer to help others  navigate toward correct answers   It might seem like debugging would highlight the problem  However  the only browser the problem occurs in is IE  and in IE you can only debug code that was part of the original document  For dynamically added code  the debugger just shows the body element as the current instruction  and IE claims the error happened on a huge line number   Here s a sample web page that will demonstrate this problem in IE    lt html gt   lt head gt   lt title gt javascript debug test lt  title gt   lt  head gt   lt body onload  attachScript     gt   lt script type  text javascript  gt  function attachScript        var s   document createElement  script       s setAttribute  type    text javascript       document body appendChild s      s text    var a   document getElementById  nonexistent    alert a tagName       lt  script gt   lt  body gt    This yielded for me the following error   Line  54654408 Error  Object required

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I too had come across this issue  I found below two solutions  1   Same as mentioned by others above  remove extra comma from JSON object  2   Also  My JSP HTML was having   Because of this it was triggering browser s old mode which was giving JS error for extra comma  When used  it triggers browser s HTML5 mode If supported  and it works fine even with Extra Comma just like any other browsers FF  Chrome etc

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Maybe you ve got an object having a method  constructor  and try to invoke that one

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This error occurs when we add or missed to remove a comma at the end of array or in function code   It is necessary to observe the entire code of a web page for such error   I got it in a Facebook app code while I was coding for a Facebook API    lt div id  fb-root  gt       lt script type  text javascript  src  http   connect facebook net en US all js  lt  script gt       lt script type  text javascript  gt            window fbAsyncInit   function                  FB init  appId     appid     status  true  cookie  true  xfbml  true                             FB Canvas setSize   width  800   height  860                                                                    extra comma here                   lt  script gt

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Had the same issue with a different configuration  This was in an angular factory definition  but I assume it could happen elsewhere as well   angular module  myModule   factory  myFactory   function        return               myMethod   function       lt --- error showing up here                          method definition                        Fix is very exotic   angular module  myModule   factory  myFactory   function        return       lt --- notice the absence of the return line         myMethod   function                            method definition

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Typescript for Windows issue  This works in IE  chrome  FF  export const OTP CLOSE      outcomeCode    OTP CLOSE       This works in chrome  FF  Does not work in IE 11  export const OTP CLOSE     outcomeCode   OTP CLOSE       I guess it somehow related to  Windows reserved words

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I came across this error where rather than a trailing comma or some such  this syntax had been used in a constants js      var titles            title X    X title          title Y    Y title          IE 11 did not like this at all   As previously mentioned though this was easily fixed by using      var titles           title X    X title         title Y    Y title

[javascript] Possible cases for Javascript error: "Expected identifier, string or number"

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