# How can I check whether an id existed?

**URL:** <https://www.ruby-forum.com/t/how-can-i-check-whether-an-id-existed/157377>\
**Category:** Rails\
**Created:** [January 10, 2009, 6:12am UTC](https://www.ruby-forum.com/t/how-can-i-check-whether-an-id-existed/157377 "2009-01-10T06:12:31Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![youhaodeyi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/b9bd4f/32.png) [@youhaodeyi](https://www.ruby-forum.com/u/youhaodeyi)\
**Post date:** [January 10, 2009, 6:12am UTC](https://www.ruby-forum.com/t/how-can-i-check-whether-an-id-existed/157377/1 "2009-01-10T06:12:31Z")

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How can I check whether an ID existed in the current page？ I want to use  
the $(‘id’).getValue() to get the field value. But sometimes the ID may  
not exist.

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<div class="post-metadata">

**Author:** ![youhaodeyi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/b9bd4f/32.png) [@youhaodeyi](https://www.ruby-forum.com/u/youhaodeyi)\
**Post date:** [January 10, 2009, 6:53am UTC](https://www.ruby-forum.com/t/how-can-i-check-whether-an-id-existed/157377/2 "2009-01-10T06:53:53Z")

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if($(‘id’)){  
val = $F(‘id’)  
}

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**Author:** ![youhaodeyi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/b9bd4f/32.png) [@youhaodeyi](https://www.ruby-forum.com/u/youhaodeyi)\
**Post date:** [January 10, 2009, 6:56am UTC](https://www.ruby-forum.com/t/how-can-i-check-whether-an-id-existed/157377/3 "2009-01-10T06:56:49Z")

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Sijo Kg wrote:

> if($(‘id’)){  
> val = $F(‘id’)  
> }

Can I put them in \*.html.erb? I got a compile error.

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<div class="post-metadata">

**Author:** ![youhaodeyi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/b9bd4f/32.png) [@youhaodeyi](https://www.ruby-forum.com/u/youhaodeyi)\
**Post date:** [January 10, 2009, 7:49am UTC](https://www.ruby-forum.com/t/how-can-i-check-whether-an-id-existed/157377/4 "2009-01-10T07:49:39Z")

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You can put either in your javascript file or enclose in

 in the html.erb file