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I am dynamically creating inputs when the users double clicks an element in a select box. There can be multiple inputs per element type, so I am creating them as HTML arrays. When the inputs are created, a link is also created that points to a javascript function. Said function will open a calendar prompt for the specific field that was clicked. I have narrowed down the issue to the below code:

document.getElementById( 'start_' + field + '[]' ).length

As you see, I am trying to grab the length of the array just like I would with a normal javascript array. This, of course, is not working. I am unable to find anything on Google referencing this, which usually means it is impossible but I find that hard to believe.

Alternatively, I can increment a variable every time this field is created I just wanted to make sure I am not missing something painfully obvious.

Thank you in advance!

{EDIT}

Please reference http://www.thefutureoftheweb.com/blog/use-arrays-with-html-form-inputs before telling me that HTML does not allow arrays.

{DoubleEdit+Answer}

The issue was not that HTML arrays do not exist, but that the ID attribute cannot be an array. I found http://roshanbh.com.np/2008/08/handling-array-html-form-elements-javascript-php.html which explains how to do what I need...ish.

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1  
You confuse id and name –  Petr Peller Aug 29 '11 at 8:43
2  
HTML doesn't have arrays, you are getting confused by PHP's form data parsing rules. You can't have multiple elements with the same id, and you can't use the caracters [ or ] in an HTML 4,x or XHTML ID. –  Quentin Aug 29 '11 at 8:46
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3 Answers

up vote 2 down vote accepted

You can use the following pure JavaScript code:

oForm = document.forms[0];
oForm.elements['start_' + field + '[]'].length;

Or in jQuery library:

$('input[name="start_' + field + '[]"]').length;

I would prefer the second because I am not 100% sure about cross-browser compatibility of the first solution.

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PERFECT! Thank you :D –  Dave Aug 29 '11 at 8:57
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up vote 1 down vote

what about using this syntax ?

onclick="myFunction( event, this )"

using this you can pass any important data - mouseposition in first parameter and object in second

in your case the syntax is invalid, during to the fact id must be unique, and foooBar[] is same id as another foooBar[] ( in fact HTML doesn't know nothing about arrays )

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This is already in the onClick function. The problem is that the element being clicked is a select box. I can parse all necessary information from this element, then I create the input box. I then need to get the length of the input box HTML array so that I can create the link to reference that specific index in the array –  Dave Aug 29 '11 at 8:44
 
You are incorrect, HTML does allow arrays and I use them all the time. It dynamically expands the array as needed, I just don't know how to access said array. If I pass the array through to PHP on the backend, I receive an array such as $_POST['input'][0], etc. The question is can javascript also access that array? –  Dave Aug 29 '11 at 8:46
 
you are wrong, this is NOT feauture of HTML, but PHP - and it is applied to name, not id - so the answer is - no , javascript cannot, because this is not parsed as array ( this is done by PHP on server ) - you can get array from document.getElementsByTagName( '*' ); ( or replace document with parent node ) –  SergeS Aug 29 '11 at 8:47
 
you got me to the right place. HTML arrays can be used in the name attribute but not in the id attribute. Thank you so much, I have accepted the answer –  Dave Aug 29 '11 at 8:50
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up vote 0 down vote

document.getElementById doesn't return a HTML Collection, so it does not have a length property.

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