Why does jQuery or a DOM method such as getElementById not find the element

Question

What are the possible reasons for document getElementById      id   or any other DOM method   jQuery selector not finding the elements   Example problems include    jQuery silently failing to bind an event handler jQuery  getter  methods   val     html     text    returning undefined A standard DOM method returning null resulting in any of several errors       Uncaught TypeError  Cannot set property       of null   Uncaught TypeError  Cannot read property       of null   The most common forms are      Uncaught TypeError  Cannot set property  onclick  of null      Uncaught TypeError  Cannot read property  addEventListener  of null      Uncaught TypeError  Cannot read property  style  of null

User · Answer

the problem is that the dom element  speclist  is not created at the time the javascript code is getting executed  So I put the javascript code inside a function and called that function on body onload event   function do this first         appending code     lt body onload  do this first    gt   lt  body gt

User · Answer

This solution is for the people who don t use jQuery and to improve performance by not moving the script to bottom of the page  and the problem is that the script is loaded before the html elements are loaded  Add your code in this function body window onload     gt               your code here         example     let element document getElementById  quot elementId quot        console log element        add everything that has to work only after the document is loaded and keep other functions that has to be executed as soon as the script is loaded outside the function  I recommend this method instead of moving down the script  because if the script is on top  the browser will try to download it as soon as it sees the script tag  if it is on the bottom of the page  it will take some more time to load it and until that time no event listeners in the script will work  in this case all other functions could be called and the window onload will get called once everything is loaded

User · Answer

My solution was to not use the id of an anchor element   lt a id  star wars  gt Place to jump to lt  a gt   Apparently blazor and other spa frameworks have issues jumping to anchors on the same page  To get around that I had to use document getElementById  star wars    However this didn t work until I put the id in a paragraph element instead   lt p id  star wars  gt Some paragraph lt p gt    Example using bootstrap    lt button class  btn btn-link  onclick  document getElementById  star wars   scrollIntoView  behavior  smooth     gt Star Wars lt  button gt       lots of other text   lt p id  star wars  gt Star Wars is an American epic    lt  p gt

User · Answer

Short and simple  Because the elements you are looking for do not exist in the document  yet      For the remainder of this answer I will use getElementById as example  but the same applies to getElementsByTagName  querySelector and any other DOM method that selects elements   Possible Reasons  There are two reasons why an element might not exist    An element with the passed ID really does not exist in the document  You should double check that the ID you pass to getElementById really matches an ID of an existing element in the  generated  HTML and that you have not misspelled the ID  IDs are case-sensitive     Incidentally  in the majority of contemporary browsers  which implement querySelector   and querySelectorAll   methods  CSS-style notation is used to retrieve an element by its id  for example  document querySelector   elementID    as opposed to the method by which an element is retrieved by its id under document getElementById  elementID    in the first the   character is essential  in the second it would lead to the element not being retrieved  The element does not exist at the moment you call getElementById    The latter case is quite common  Browsers parse and process the HTML from top to bottom  That means that any call to a DOM element which occurs before that DOM element appears in the HTML  will fail   Consider the following example    lt script gt      var element   document getElementById  my element     lt  script gt    lt div id  my element  gt  lt  div gt    The div appears after the script  At the moment the script is executed  the element does not exist yet and getElementById will return null   jQuery  The same applies to all selectors with jQuery  jQuery won t find elements if you misspelled your selector or you are trying to select them before they actually exist   An added twist is when jQuery is not found because you have loaded the script without protocol and are running from file system    lt script src    somecdn somewhere com jquery min js  gt  lt  script gt    this syntax is used to allow the script to load via HTTPS on a page with protocol https    and to load the HTTP version on a page with protocol http     It has the unfortunate side effect of attempting and failing to load file   somecdn somewhere com       Solutions  Before you make a call to getElementById  or any DOM method for that matter   make sure the elements you want to access exist  i e  the DOM is loaded   This can be ensured by simply putting your JavaScript after the corresponding DOM element   lt div id  my element  gt  lt  div gt    lt script gt      var element   document getElementById  my element     lt  script gt    in which case you can also put the code just before the closing body tag   lt  body gt    all DOM elements will be available at the time the script is executed    Other solutions include listening to the load  MDN  or DOMContentLoaded  MDN  events  In these cases it does not matter where in the document you place the JavaScript code  you just have to remember to put all DOM processing code in the event handlers   Example   window onload   function            process DOM elements here        or     does not work IE 8 and below document addEventListener  DOMContentLoaded   function            process DOM elements here       Please see the articles at quirksmode org for more information regarding event handling and browser differences   jQuery  First make sure that jQuery is loaded properly  Use the browser s developer tools to find out whether the jQuery file was found and correct the URL if it wasn t  e g  add the http  or https  scheme at the beginning  adjust the path  etc    Listening to the load DOMContentLoaded  events is exactly what jQuery is doing with  ready    docs   All your jQuery code that affects DOM element should be inside that event handler   In fact  the jQuery tutorial explicitly states      As almost everything we do when using jQuery reads or manipulates the document object model  DOM   we need to make sure that we start adding events etc  as soon as the DOM is ready       To do this  we register a ready event for the document     document  ready function           do stuff when DOM is ready        Alternatively you can also use the shorthand syntax     function            do stuff when DOM is ready       Both are equivalent

User · Answer

As  FelixKling pointed out  the most likely scenario is that the nodes you are looking for do not exist  yet    However  modern development practices can often manipulate document elements outside of the document tree either with DocumentFragments or simply detaching reattaching current elements directly   Such techniques may be used as part of JavaScript templating or to avoid excessive repaint reflow operations while the elements in question are being heavily altered   Similarly  the new  Shadow DOM  functionality being rolled out across modern browsers allows elements to be part of the document  but not query-able by document getElementById and all of its sibling methods  querySelector  etc    This is done to encapsulate functionality and specifically hide it   Again  though  it is most likely that the element you are looking for simply is not  yet  in the document  and you should do as Felix suggests  However  you should also be aware that that is increasingly not the only reason that an element might be unfindable  either temporarily or permanently

User · Answer

The element you were trying to find wasn   t in the DOM when your script ran   The position of your DOM-reliant script can have a profound effect upon its behavior  Browsers parse HTML documents from top to bottom  Elements are added to the DOM and scripts are  generally  executed as they re encountered  This means that order matters  Typically  scripts can t find elements which appear later in the markup because those elements have yet to be added to the DOM   Consider the following markup  script  1 fails to find the  lt div gt  while script  2 succeeds    x000D   x000D   lt script gt  x000D    console log  script  1   o   document getElementById  test        null x000D   lt  script gt  x000D   lt div id  test  gt test div lt  div gt  x000D   lt script gt  x000D    console log  script  2   o   document getElementById  test         lt div id  test      x000D   lt  script gt  x000D   x000D   x000D    So  what should you do  You ve got a few options     Option 1  Move your script  Move your script further down the page  just before the closing body tag  Organized in this fashion  the rest of the document is parsed before your script is executed    x000D   x000D   lt body gt  x000D     lt button id  test  gt click me lt  button gt  x000D     lt script gt  x000D      document getElementById  test   addEventListener  click   function     x000D        console log  clicked   o   this   x000D          x000D     lt  script gt  x000D   lt  body gt  lt  -- closing body tag -- gt  x000D   x000D   x000D    Note  Placing scripts at the bottom is generally considered a best practice     Option 2  jQuery s ready    Defer your script until the DOM has been completely parsed  using   handler     x000D   x000D   lt script src  https   ajax googleapis com ajax libs jquery 2 1 1 jquery min js  gt  lt  script gt  x000D   lt script gt  x000D      function     x000D          test   click function     x000D        console log  clicked   o   this   x000D          x000D        x000D   lt  script gt  x000D   lt button id  test  gt click me lt  button gt  x000D   x000D   x000D    Note  You could simply bind to DOMContentLoaded or  window onload but each has its caveats  jQuery s ready   delivers a hybrid solution     Option 3  Event Delegation     Delegated events have the advantage that they can process events from descendant elements that are added to the document at a later time    When an element raises an event  provided that it s a bubbling event and nothing stops its propagation   each parent in that element s ancestry receives the event as well  That allows us to attach a handler to an existing element and sample events as they bubble up from its descendants    even those added after the handler is attached  All we have to do is check the event to see whether it was raised by the desired element and  if so  run our code    jQuery s on   performs that logic for us  We simply provide an event name  a selector for the desired descendant  and an event handler    x000D   x000D   lt script src  https   ajax googleapis com ajax libs jquery 2 1 1 jquery min js  gt  lt  script gt  x000D   lt script gt  x000D      document  on  click     test   function e    x000D      console log  clicked   o    this   x000D        x000D   lt  script gt  x000D   lt button id  test  gt click me lt  button gt  x000D   x000D   x000D    Note  Typically  this pattern is reserved for elements which didn t exist at load-time or to avoid attaching a large amount of handlers  It s also worth pointing out that while I ve attached a handler to document  for demonstrative purposes   you should select the nearest reliable ancestor     Option 4  The defer attribute  Use the defer attribute of  lt script gt        defer  a Boolean attribute   is set to indicate to a browser that the script is meant to be executed after the document has been parsed  but before firing DOMContentLoaded     x000D   x000D   lt script src  https   gh-canon github io misc-demos log-test-click js  defer gt  lt  script gt  x000D   lt button id  test  gt click me lt  button gt  x000D   x000D   x000D    For reference  here s the code from that external script   document getElementById  test   addEventListener  click   function e      console log  clicked   o   this          Note  The defer attribute certainly seems like a magic bullet but it s important to be aware of the caveats    1  defer can only be used for external scripts  i e   those having a src attribute  2  be aware of browser support  i e   buggy implementation in IE  lt  10

User · Answer

If the element you are trying to access is inside an iframe and you try to access it outside the context of the iframe this will also cause it to fail   If you want to get an element in an iframe you can find out how here

User · Answer

When I tried your code  it worked   The only reason that your event is not working  may be that your DOM was not ready and your button with id  event-btn  was not yet ready  And your javascript got executed and tried to bind the event with that element   Before using the DOM element for binding  that element should be ready  There are many options to do that   Option1  You can move your event binding code within document ready event  Like   document addEventListener  DOMContentLoaded    event    gt        your code to bind the event       Option2  You can use timeout event  so that binding is delayed for few seconds  like   setTimeout function        your code to bind the event    500     Option3  move your javascript include to the bottom of your page   I hope this helps you

User · Answer

Reasons why id based selectors don t work   The element DOM with id specified doesn t exist yet  The element exists  but it is not registered in DOM  in case of HTML nodes appended dynamically from Ajax responses   More than one element with the same id is present which is causing a conflict    Solutions   Try to access the element after its declaration or alternatively use stuff like   document  ready    For elements coming from Ajax responses  use the  bind   method of jQuery  Older versions of jQuery had  live   for the same  Use tools  for example  webdeveloper plugin for browsers  to find duplicate ids and remove them

User · Answer

If script execution order is not the issue  another possible cause of the problem is that the element is not being selected properly   getElementById requires the passed string to be the ID verbatim  and nothing else  If you prefix the passed string with a    and the ID does not start with a    nothing will be selected     lt div id  quot foo quot  gt  lt  div gt           Error  selected element will be null    document getElementById   foo        Fix    document getElementById  foo     Similarly  for getElementsByClassName  don t prefix the passed string with a       lt div class  quot bar quot  gt  lt  div gt           Error  selected element will be undefined    document getElementsByClassName   bar   0       Fix    document getElementsByClassName  bar   0    With querySelector  querySelectorAll  and jQuery  to match an element with a particular class name  put a   directly before the class  Similarly  to match an element with a particular ID  put a   directly before the ID     lt div class  quot baz quot  gt  lt  div gt           Error  selected element will be null    document querySelector  baz        baz        Fix    document querySelector   baz         baz    The rules here are  in most cases  identical to those for CSS selectors  and can be seen in detail here   To match an element which has two or more attributes  like two class names  or a class name and a data- attribute   put the selectors for each attribute next to each other in the selector string  without a space separating them  because a space indicates the descendant selector   For example  to select     lt div class  quot foo bar quot  gt  lt  div gt   use the query string  foo bar  To select    lt div class  quot foo quot  data-bar  quot someData quot  gt  lt  div gt   use the query string  foo data-bar  quot someData quot    To select the  lt span gt  below     lt div class  quot parent quot  gt       lt span data-username  quot bob quot  gt  lt  span gt     lt  div gt   use div parent  gt  span data-username  quot bob quot     Capitalization and spelling does matter for all of the above  If the capitalization is different  or the spelling is different  the element will not be selected     lt div class  quot result quot  gt  lt  div gt           Error  selected element will be null    document querySelector   results         Result        Fix    document querySelector   result         result     You also need to make sure the methods have the proper capitalization and spelling  Use one of    selector  document querySelector document querySelectorAll document getElementsByClassName document getElementsByTagName document getElementById  Any other spelling or capitalization will not work  For example  document getElementByClassName will throw an error   Make sure you pass a string to these selector methods  If you pass something that isn t a string to querySelector  getElementById  etc  it almost certainly won t work   If the HTML attributes on elements you want to select are surrounded by quotes  they must be plain straight quotes  either single or double   curly quotes like     or     will not work if you re trying to select by ID  class  or attribute

[javascript] Why does jQuery or a DOM method such as getElementById not find the element?

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