Checking Existence Of An Element?

Jul 20, 2005

Is it possible to check for the existence of an element? I have a dynamic
page which may or may not have a <div> holding a bunch of thumbnails, and I
want a function to check for the existence of the <div>. Doing:

blah = getElementById("thumbnails");

Generates an error.... I was hoping it would just return false or
something... Is there a way of doing this?

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JQuery :: Checking For The Existence Of An Appended Object?

Sep 27, 2011

Here's what I want to happen with the above: "if txComments is there don't append it again"owever when I run this code, it appends a new "txComments" every time the code is triggered.

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JQuery :: Checking For Existence Of A <td> Class Name In Dynamically Created Table?

Feb 27, 2010

checks my table (previously created by "click handler") "td" elements for not existance of a paticular class name.

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Testing For Existence Of Element?

Apr 13, 2010

I have the following code:

<script language="javascript">
// Max number of items to show/hide


Which is designed to hide all but one of a group of DIVs with consecutive IDs in the form "listings_stations_<number>". The problem is, I won't know how many of these DIVS there will be. I know a maximum possible number though.

The script as-is works, but obviously throws up errors trying to get handles to non-existent elements/objects. How can I check an element exists before getting and setting style properties for it? I'd like a solution that works for all three browser-types the script currently works with.

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Checking If Element Is In The Node Of Another Element

Jul 23, 2005

Has anybody seen a function which checked if one of passed elements is
nested in the node of another element passed to function, no matter how deep
it is nested ?

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Checking Next Element

Sep 27, 2006

I'm trying to run some code when a H2 element is clicked on an unordered list below it. The problem is, the code runs whether the h2 has a ul below it or not.

h[x].onclick = function(){
var ul = this.nextSibling;

while (ul.nodeType != 1){
ul = ul.nextSibling;

So, if I have something like this:

<h2>Subtitle 2</h2>

Clicking "Subtitle" runs the function on "Subtitle 2". I don't want the function to run unless the next element is an ul. How can I verify that the next element is an unordered list and if not, don't run anything?

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JQuery :: Checking The Last Element ?

Dec 16, 2011


This is the code i created i wonder how can i check if the last element has been selected and how to go start at first element.

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JQuery :: Checking For A CSS Property On An Element?

Aug 18, 2011

I would like to be able to test if an element already has a style applied to it. This style might either be an inline style, or come from a stylesheet. I'm writing a plugin which needs to apply a CSS style to an element if it's not already there.

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Checking To See If Element Created With CreateElement Exists

Sep 16, 2009

I'm trying to check to see if a dynamically created element exists BEFORE creating another element of the same exact type...but my if statement at the beginning is not working and another element is just created.

function writeElement(id) {
if(document.getElementsByTagName('transElement')[0]) {
var id = id;
var id = id;
var transElement = document.createElement('transElement');

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Checking Element Existance In Foreign Page

Jun 5, 2010

[code]so now if url is xyz.html, the i'm getting the content of that page through AJAX and loading it to a DIV element(x).....and then accessing the div elements "name","category" etc.,but if urls point to heavy pages, it's slow process to do this work. so I WANT TO CHECK WHETHER THOSE DIV ID's EXIST IN THAT PAGE OR NOT WITHOUT LOADING THEM and then GET THEIR VALUES IF EXISTS.

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How To Check URL Existence ?

Aug 24, 2006

I have the following HTML code which is doing a GET to a page, say
MyUrl.aspx :

<form name="form1" method="get" action="MyUrl.aspx" id="form1">
<input type="hidden" name="ClickedElement" id="Messenger" />

where the the Submit() is done within a javascript function invoked at
onclick on some element.

My question is: How can I prevent form submission when MyUrl.aspx is
not available? The javascript function is:

function Clicked(MyControl)
var _CellContent = document.getElementById("Messenger");
_CellContent.value =;

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Possible To Check Existence Of XML?

Sep 25, 2006

Is there any possibility to check the existence of XML?

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Word Existence

Aug 23, 2001

How do I check if a certain word exists in a text box? For example, if I set the word to be found to "word1", if the text box is "This is word1", and alert would come up saying that "word1" was found.

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Validating Existence Of XML Tag ?

Apr 13, 2011

I am creating this Javascript/XML HTA that is basically a project tracker. I recently added some new fields in the form that are written to the XML file for the project being tracked. This makes the files neither backwards compatible if I use it in a previous version nor forward compatible for future versions. This means if a user is using version 1, I create version 2, he wants to import his old tasks to Version 2, it throws an error. For example if I have a <status> element written in the newest version, but no <status> in the previous, I can no longer use that projects XML file in a previous version.

I tried to use the following code to validate existence of the tag and assign whatever outcome as the variable to write, but it's not working. Theres a few different ways I tried.

1st Way:


2nd Way:


3rd Way:


Here's the XML file for reference.


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Existence Of Several Global Variables

Jul 20, 2005

Suppose I have global variables: x1, x2, x3
and I have a function that needs to assign a value to a new global variable

something like
function foo ()
count = 0;
do {
count ++
varname = 'x'+ count
} while (globalExists (varname)

eval ( varname + ' = "I am new in the x-series" ' )

how would the function globalExists () be implemented ?

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Toggle Not Just Visibility, But Existence?

Feb 19, 2009

I'd like to be able to toggle the existence of a DIV using the onclick attribute.

HTML Code:
<input type="radio" value="1" checked="checked"
onclick="document.getElementById('div').style.visibility='hidden';"> 1


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Check An External Url Existence?

Sep 22, 2011

I need to check the whether an external url like exists or not using javascript.

I have a ajax method for it,

function checkUrl(url) {
var xmlhttp=false;
if (!xmlhttp && typeof XMLHttpRequest!='undefined') {


But is not successful for finding existence of external urls.

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Test For Existence Of Dynamic Variable

Mar 26, 2006

I am using Javascript to add rows to tables, etc. in a function I am
calling. I pass the function the ID of the div, and what I want in the
rows, and it will add rows to a table in the div.

The problem is I need to test for the existence of the table - and if
the variable or object doesn't exist already my code errors -
PLEASE REMEMBER - I don't know the name of the variable or object I am
testing the existance for - it is created dynamically based on the
divID. So when I test for this object or variable the test has to be
for a dynamically created object - Code:

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Check For The Existence Of A Variable With A Calculated Name?

Jan 29, 2009

I'm processing a form with numbered fields, but I don't know how many fields there are. Might be 1, might be 20. So I'm iterating through 1-20 and trying the following test:

for(i=1; i<=20; i++) {
if(typeof(eval('document.edit_orderitem_form.field_'+i+'.value')) != 'undefined') {
[doing stuff with the form field here]

The script quits on that line with "Undefined value" showing up in Safari's error console. I just can't figure out how to eval() the name of a field when it may or may not exist.

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Testing Image Existence With Side-effects

Oct 5, 2005

I'm trying to write a function to determine whether or not an image exists.

Most people recommend setting the onload event handler. That works like a
charm except that side-effective actions seem to be impossible. I can, as
nearly as I can tell, run alert and opera.postError (I test on IE, firefox,
and opera by the way). I've tried using the 'this' while in the event
handler, setting,, window.document.getElementById(test's
id).name. I just can't seem to find any means of using side effects inside
the event handler.

Below are several examples of things I've tried so far:

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Disable/enable Submit Button Based On Existence Of Validation Errors?

May 1, 2010

Would anyone care to post your favorite script for disabling the submit button on a form when there are input errors, and reenabling when all errors are resolved? I'd be curious what the different approaches are to this. I looked through my various SitePoint javascript books and surprisingly didn't find an answer to this scenario specifically.The behavior I'm trying to achieve (most efficiently) is having a form start out with the submit button enabled, but if there is a validation error, such as a required field being left blank on blur, the submit button is disabled. It's easy then to re-enable it when the user fills in that field, but harder to get the script to check and see if there are any other lingering errors before going ahead and enabling it.

My natural inclination would be to just keep a count of errors that increments and decrements when errors occur and are resolved. Then the script would check to see that the error count is 0 before re-enabling the submit button. It seemed easy, but I think I'm getting mixed up somewhere in conflicts of variable scope, and it's not turning out right.A google search rendered an example where someone was using a string variable to store errors, concatenating and replacing data to the string as errors were logged/resolved.

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Pass Text From One Select Box To Another Select Box Using The For Loop To Check The Existence Of An Item But It Is Not Working?

Aug 28, 2010

i am trying to pass text from one select box to another select box. The logic is if 10 are added, no more passing must happen. Also if an item is already added, it mustn't be added again.I am using the for loop to check the existence of an item but it is not working: what am i doing wrong?

function PassSelectValues(){
//pass values from select boxes to select boxes
var counter;[code]....

why isn't counter incrementing at all? The alert message box does appear saying item exists but the item gets added anyway.

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JQuery :: Way To Highlight Element Inside Parent Element / When Mouse Hovers Over Child Element?

Oct 4, 2010

i have a menu generated by a list with nested lists. i want the parent link to stay highlighted when the mouse hovers over the sub menus. because those sub menus are also generated by jquery (qtip), CSS alone won't do it (triedul.topnav li:hover a {background-color: #F00;}).is there a way to do this using jquery?

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Checking Parent's URL ?

Jul 23, 2005

How can i check parent's URL from a child (popup) window ? and how can i
refresh it if the URL is say

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Image Checking

Jan 9, 2006

I have some javascript that uses setInterval(..) to change the src of
an image every second. Is there any way of programmatically checking to
see whether an image is loaded properly or if a 404 File Not Found
error occurs for it?

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Argument Checking

Aug 8, 2006

Does anyone have any coding rules they follow when doing argument checking?

When arguments fail during check, do you return from the call with an ambiguous return value, or do you throw exceptions?

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