How can I check whether an id existed?

Rails
1

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.

2

if($(‘id’)){
val = $F(‘id’)
}

3

Sijo Kg wrote:

if($(‘id’)){
val = $F(‘id’)
}

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

4

You can put either in your javascript file or enclose in

in the html.erb file