TypeError Cannot read property 0 from undefined

Question

I m getting a very weird undefined error   function login name pass      var blob   Utilities newBlob pass     var passwordencode   Utilities base64Encode blob getBytes       var ss   SpreadsheetApp openById        var sheet   ss getActiveSheet      var data   sheet getDataRange   getValues      var i 1    while  name    data i  0        Logger log data i  0        i          if  passwordencode    data i  1        UserProperties setProperties          name   name         pass    passwordencode               Logger log  You are logged in          else if  passwordencode    data i  1         Logger log  You are not logged in        UserProperties setProperties          name               pass                         using googlescript  The one that s undefined is the while statement where while name    data i  0   claiming that you cannot read property  0  from undefined  What s weird about this  If I remove the data i  0  in the while statement  it still works in the logger log  And everywhere else  What the heck is going on   EDIT  If I change the while to a if statement it also works

User · Answer

The while increments the i  So you get   data 1  0  data 2  0  data 3  0        It looks like name doesn t match any of the the elements of data  So  the while still increments and you reach the end of the array  I ll suggest to use for loop

User · Answer

Looks like what you re trying to do is access property  0  of an undefined value in your  data  array   If you look at your while statement  it appears this is happening because you are incrementing  i  by 1 for each loop  Thus  the first time through  you will access   data 1    but on the next loop  you ll access  data 2   and so on and so forth  regardless of the length of the array   This will cause you to eventually hit an array element which is undefined  if you never find an item in your array with property  0  which is equal to  name      Ammend your while statement to this       for var iIndex   1  iIndex  lt   data length  iIndex         if  data iIndex  0      name            break             Logger log data i  0

User · Answer

Check your array index to see if it s accessed out of bound   Once I accessed categories 0   Later I changed the array name from categories to category but forgot to change the access point--from categories 0  to category 0   thus I also get this error   JavaScript does a poor debug message  In your case  I reckon probably the access gets out of bound

User · Answer

For me  the problem was I was using a package that isn t included in package json nor installed  import   ToastrService   from  ngx-toastr    So when the compiler tried to compile this  it threw an error   I installed it locally  and when running a build on an external server the error was thrown

User · Answer

Under normal circumstances out of bound of array when you encounter the error  So check uo your array subscript

[javascript] TypeError: Cannot read property "0" from undefined

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