Check if AJAX response data is empty blank null undefined 0

Question

What I have   I have jQuery AJAX function that returns HTML after querying a database  Depending on the result of the query  the function will either return HTML code or nothing  i e  blank  as desired   What I need   I need to conditionally check for when the data is blank   My code     ajax       type  POST       url    lt  php echo admin url  admin-ajax php      gt        data  associated buildsorprojects form      success function data           if  data               if data  undefined              if data    undefined              if data  null             if data length    0             if   data length    0              if data   0             if data    0                   alert  Data      data                        error  function errorThrown           alert errorThrown           alert  There is an error with AJAX                                My problem   I ve tried a variety of conditions but none correctly check the data  Based on my findings  a blank alert message does not mean data is    empty non-existent equal to zero of length zero null undefined   If it s none of these things  how can I therefore conditionally check for the data that yields a blank alert message

User · Answer

This worked form me    PHP Code on page php    query de  sql statements here     sql de   sqlsrv query  conn  query de         if   sql de                  echo  SQLSuccess                     exit      and then AJAX Code has bellow  jQuery ajax                       url     page php                       type    POST                       data                                 buttonsave     1                              var1           val1                              var2           val2                                                     success function data                                                    if jQuery trim data       SQLSuccess                                                                   alert  Se agrego correctamente                                 alert data                                           else   alert data                                                        error  function error                                                   alert  Error AJAX not working     error                                                           NOTE  the word  SQLSuccess  must be received from PHP

User · Answer

if data trim        alert  Nothing Found

User · Answer

if data  undefined      This is an assignment statement  not a comparison  Also   undefined  is a string  it s a property  Checking it is like this  if  data     undefined   no quotes  otherwise it s a string value   If it s not defined  you may be returning an empty string  You could try checking for a falsy value like if   data  as well

User · Answer

The following correct answer was provided in the comment section of the question by Felix Kling   if     trim data           alert  What follows is blank      data     else         alert  What follows is not blank      data

User · Answer

ajax       type  POST       url    lt  php echo admin url  admin-ajax php      gt        data  associated buildsorprojects form      success function data              do console log data           console log data              you ll find that what exactly inside data             I do not prefer alter data   now because  it does not             completes requirement all the time             After that you can easily put if condition that you do not want like            if data                   if data    null             or whatever you want             error  function errorThrown           alert errorThrown           alert  There is an error with AJAX

[javascript] Check if AJAX response data is empty/blank/null/undefined/0

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