How to check null objects in jQuery

Question

I m using jQuery and I want to check the existence of an element in my page  I have written following code  but it s not working   if     btext    i     null          alert     btext    i  text             btext    i  text  Branch     i       How do I check the existence of the element

User · Answer

no matter what you selection is the function     always returns a jQuery object so that cant be used to test  The best way yet  if not the only  is to use the size   function or the native length property as explained above   if      selector   size

User · Answer

if       whatever   0            The jQuery object which is returned by all native jQuery methods is NOT an array  it is an object with many properties  one of them being a  length  property  You can also check for size   or get 0  or get   -  get 0   works the same as accessing the first element  i e    elem  0

User · Answer

Calling length property on undefined or a null object will cause IE and webkit browsers to fail   Instead try this   if     something       null        do something     or  if     something       null        don t do something

User · Answer

The lookup function returns an array of matching elements   You could check if the length is zero   Note the change to only look up the elements once and reuse the results as needed   var elem       btext    i   if  elem length    0       elem text  Branch     i       Also  have you tried just using the text function -- if no element exists  it will do nothing       btext    i  text  Branch     i

User · Answer

if  typeof     btext    i       object            btext    i  text  Branch     i

User · Answer

In jQuery 1 4 you get the   isEmptyObject function  but if you are forced to use an older version of jQ like us poor Drupal developers just steal use this code      This is a function similar to the jQuery 1 4   isEmptyObject  function isObjectEmpty obj      for   var name in obj         return false        return true      Use it like   console log isObjectEmpty the object       Returns true or false

User · Answer

if  typeof     btext    i       object            btext    i  text  Branch     i

User · Answer

jquery     function always return non null value - mean elements matched you selector cretaria  If the element was not found it will return an empty array   So your code will look something like this -   if      btext    i  length             alert     btext    i  text             btext    i  text  Branch     i

User · Answer

What about using  undefined    if  value    undefined      do stuff

User · Answer

The lookup function returns an array of matching elements   You could check if the length is zero   Note the change to only look up the elements once and reuse the results as needed   var elem       btext    i   if  elem length    0       elem text  Branch     i       Also  have you tried just using the text function -- if no element exists  it will do nothing       btext    i  text  Branch     i

User · Answer

The lookup function returns an array of matching elements   You could check if the length is zero   Note the change to only look up the elements once and reuse the results as needed   var elem       btext    i   if  elem length    0       elem text  Branch     i       Also  have you tried just using the text function -- if no element exists  it will do nothing       btext    i  text  Branch     i

User · Answer

Check the jQuery FAQ     You can use the length property of the jQuery collection returned by your selector   if       myDiv   length

User · Answer

jquery     function always return non null value - mean elements matched you selector cretaria  If the element was not found it will return an empty array   So your code will look something like this -   if      btext    i  length             alert     btext    i  text             btext    i  text  Branch     i

User · Answer

In jQuery 1 4 you get the   isEmptyObject function  but if you are forced to use an older version of jQ like us poor Drupal developers just steal use this code      This is a function similar to the jQuery 1 4   isEmptyObject  function isObjectEmpty obj      for   var name in obj         return false        return true      Use it like   console log isObjectEmpty the object       Returns true or false

User · Answer

when the object is empty return this error   Uncaught TypeError  Cannot read property  0  of null   I try this code    try    if      btext    i  length                      catch err     if      btext    i  length           working this code if the item  not NULL

User · Answer

What about using  undefined    if  value    undefined      do stuff

User · Answer

if       whatever   0            The jQuery object which is returned by all native jQuery methods is NOT an array  it is an object with many properties  one of them being a  length  property  You can also check for size   or get 0  or get   -  get 0   works the same as accessing the first element  i e    elem  0

User · Answer

Check the jQuery FAQ     You can use the length property of the jQuery collection returned by your selector   if       myDiv   length

User · Answer

if       whatever   0            The jQuery object which is returned by all native jQuery methods is NOT an array  it is an object with many properties  one of them being a  length  property  You can also check for size   or get 0  or get   -  get 0   works the same as accessing the first element  i e    elem  0

User · Answer

Using the length property you can do this   jQuery fn exists   function   return    this  length  lt  0    if    selector  exists            do somthing

User · Answer

if       whatever   0            The jQuery object which is returned by all native jQuery methods is NOT an array  it is an object with many properties  one of them being a  length  property  You can also check for size   or get 0  or get   -  get 0   works the same as accessing the first element  i e    elem  0

User · Answer

use     selector   get 0  to check with null like that  get returns the dom element  until then you re dealing with an array  where you need to check the length property  I personally don t like length check for null handling  it confuses me for some reason

User · Answer

use     selector   get 0  to check with null like that  get returns the dom element  until then you re dealing with an array  where you need to check the length property  I personally don t like length check for null handling  it confuses me for some reason

User · Answer

Since I don t seem to have enough reputation to vote down the answer      Wolf wrote      Calling length property on undefined   or a null object will cause IE and   webkit browsers to fail       Instead try this       NOTE   THE FOLLOWING IS WRONG  DO NOT USE   -- EleotleCram if     something       null        do something         or      NOTE   THE FOLLOWING IS WRONG  DO NOT USE   -- EleotleCram if     something       null        don t do something      While it is true that calling the length property on an undefined or null object will cause browsers to fail  the result of jQuery s selectors  the           will never be null or undefined  Thus the code suggestions make no sense  Use one of the other answers  they make more sense      Update 2012  Because people look at code and this answer is pretty high up the list  For the last couple of years  I have been using this small plugin     jQuery fn  any     function          return  this length  gt  0          I think    div   any   reads better than    div   length  plus you won t suffer as much from typos     div   ayn   will give a runtime error     div   lenght will silently most likely always be falsy      Edits november 2012   1  Because people tend to look at code and not read what is said around the code  I added two big caveat lector notes to the quoted code of Wolf  2  I added code of the small plugin I use for this situation

User · Answer

no matter what you selection is the function     always returns a jQuery object so that cant be used to test  The best way yet  if not the only  is to use the size   function or the native length property as explained above   if      selector   size

User · Answer

Using the length property you can do this   jQuery fn exists   function   return    this  length  lt  0    if    selector  exists            do somthing

User · Answer

when the object is empty return this error   Uncaught TypeError  Cannot read property  0  of null   I try this code    try    if      btext    i  length                      catch err     if      btext    i  length           working this code if the item  not NULL

User · Answer

The lookup function returns an array of matching elements   You could check if the length is zero   Note the change to only look up the elements once and reuse the results as needed   var elem       btext    i   if  elem length    0       elem text  Branch     i       Also  have you tried just using the text function -- if no element exists  it will do nothing       btext    i  text  Branch     i

User · Answer

Check the jQuery FAQ     You can use the length property of the jQuery collection returned by your selector   if       myDiv   length

User · Answer

jquery     function always return non null value - mean elements matched you selector cretaria  If the element was not found it will return an empty array   So your code will look something like this -   if      btext    i  length             alert     btext    i  text             btext    i  text  Branch     i

User · Answer

jquery     function always return non null value - mean elements matched you selector cretaria  If the element was not found it will return an empty array   So your code will look something like this -   if      btext    i  length             alert     btext    i  text             btext    i  text  Branch     i

User · Answer

Since I don t seem to have enough reputation to vote down the answer      Wolf wrote      Calling length property on undefined   or a null object will cause IE and   webkit browsers to fail       Instead try this       NOTE   THE FOLLOWING IS WRONG  DO NOT USE   -- EleotleCram if     something       null        do something         or      NOTE   THE FOLLOWING IS WRONG  DO NOT USE   -- EleotleCram if     something       null        don t do something      While it is true that calling the length property on an undefined or null object will cause browsers to fail  the result of jQuery s selectors  the           will never be null or undefined  Thus the code suggestions make no sense  Use one of the other answers  they make more sense      Update 2012  Because people look at code and this answer is pretty high up the list  For the last couple of years  I have been using this small plugin     jQuery fn  any     function          return  this length  gt  0          I think    div   any   reads better than    div   length  plus you won t suffer as much from typos     div   ayn   will give a runtime error     div   lenght will silently most likely always be falsy      Edits november 2012   1  Because people tend to look at code and not read what is said around the code  I added two big caveat lector notes to the quoted code of Wolf  2  I added code of the small plugin I use for this situation

User · Answer

Calling length property on undefined or a null object will cause IE and webkit browsers to fail   Instead try this   if     something       null        do something     or  if     something       null        don t do something

User · Answer

Check the jQuery FAQ     You can use the length property of the jQuery collection returned by your selector   if       myDiv   length

[javascript] How to check null objects in jQuery

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