Cannot read property push of undefined when combining arrays

Question

When pushing an array s contents to another array I get       Uncaught TypeError  Cannot read property  push  of undefined  error   in this snippet    var order   new Object    stack       for var i 0 i lt a length i         if parseInt a i  daysleft     0   order 0  push a i          if parseInt a i  daysleft   gt  0   order 1  push a i          if parseInt a i  daysleft   lt  0   order 2  push a i          Why do I get this error in the second if statement   Thanks a lot

User · Answer

In most cases you have to initialize the array   let list  number

User · Answer

You do not need to give an index    Instead of doing order 0  push a i    just do order push a i

User · Answer

You get the error because order 1  is undefined    That error message means that somewhere in your code  an attempt is being made to access a property with some name  here it s  push    but instead of an object  the base for the reference is actually undefined   Thus  to find the problem  you d look for code that refers to that property name   push    and see what s to the left of it  In this case  the code is  if parseInt a i  daysleft   gt  0   order 1  push a i        which means that the code expects order 1  to be an array  It is  however  not an array  it s undefined  so you get the error  Why is it undefined  Well  your code doesn t do anything to make it anything else  based on what s in your question   Now  if you just want to place a i  in a particular property of the object  then there s no need to call  push   at all   var order       stack       for var i 0 i lt a length i         if parseInt a i  daysleft     0   order 0    a i         if parseInt a i  daysleft   gt  0   order 1    a i         if parseInt a i  daysleft   lt  0   order 2    a i

User · Answer

Generally  Push method is used to add elements at the end of an array  Here  you have used the push method to an object and not an array which is  order   Steps to debug    Change the object into an empty array  var order       stack        Now you can use the push method for this array as usual  To use push method to this  order  array  you should not use the array index when calling push method to an array  Just use the name of the array only  var order       stack        for var i   0  i lt a length  i         if parseInt a i  daysleft     0         order push a i              if parseInt a i  daysleft   gt  0         order push a i              if parseInt a i  daysleft   lt  0         order push a i

User · Answer

order   is undefined that s why  Just define order 1     n  to   some value  this should fix it

User · Answer

I fixed in the below way with typescript   Define and initialize firest   pageNumbers  number           than populate it  for  let i   1  i  lt  201  i          this pageNumbers push i

User · Answer

order is an Object  not an Array     push   is for arrays   Refer to this post  Try this though but your subobjects have to be Arrays      var order   new Array        initialize order  n   index order n    new Array        and then you can perform push   order n  push some value     Or you can just use order as an array of non-array objects   var order   new Array     order push a n

User · Answer

answer to your question is simple order is not a object make it an array  var order   new Array    order push  item to push    when ever this error appears just check the left of which property the error is in this case it is push which is order   so it is undefined

User · Answer

This error occurs in angular when you didn t intialise the array blank  For an example  userlist  any     this userlist          or userlist  any

[javascript] Cannot read property 'push' of undefined when combining arrays

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