javascript - RJS: Check for existing page element? - Stack Overflow

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I have a textfield with the id "foo" that sometimes exists and sometimes not. If it exists I'd like to fill in a certain value.

How do you do this by using RJS (in Rails 2.2)?

I tried this and it doesn't work:

if page[:foo]
  page[:foo].value = "bar"
end

I get

TypeError: Null Value if the textfield doesn't exist

.

I have a textfield with the id "foo" that sometimes exists and sometimes not. If it exists I'd like to fill in a certain value.

How do you do this by using RJS (in Rails 2.2)?

I tried this and it doesn't work:

if page[:foo]
  page[:foo].value = "bar"
end

I get

TypeError: Null Value if the textfield doesn't exist

.

• javascript
• ruby-on-rails
• prototype
• rjs

Share Improve this question Follow edited Feb 1, 2016 at 16:53 Sameera R. 4,59222 gold badges3939 silver badges5353 bronze badges asked Mar 10, 2009 at 14:57 JavierJavier 2,53144 gold badges3737 silver badges5757 bronze badges

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 6

I've e up on this many times where I have a conditional item that needs to be acted upon if it exists. Using page.select avoids the Null Value error.

  page.select('#dom_object_id').each do |element|
    element.value = "bar"
  end

I put this in my *.js.rjs file. When the select sends an empty array to each it returns nothing instead of the TypeError you'd get when directly selecting by id when no DOM object with the correct ID is on the page.

I don't think you can from RJS. As a workaround, you can simply call a javascript method from RJS that checks if the element exists.

page << "update_foo('#{my_value}');"

Javascript ..

function update_foo(val)
{
  if( $('foo') != undefined )
  {
    $('foo').value = 'bar';
  } 
}

Edit

Fixed the ruby part..

I have a textfield with the id "foo" that sometimes exists and sometimes not. If it exists I'd like to fill in a certain value.

How do you do this by using RJS (in Rails 2.2)?

I tried this and it doesn't work:

if page[:foo]
  page[:foo].value = "bar"
end

I get

TypeError: Null Value if the textfield doesn't exist

.

I have a textfield with the id "foo" that sometimes exists and sometimes not. If it exists I'd like to fill in a certain value.

How do you do this by using RJS (in Rails 2.2)?

I tried this and it doesn't work:

if page[:foo]
  page[:foo].value = "bar"
end

I get

TypeError: Null Value if the textfield doesn't exist

.

• javascript
• ruby-on-rails
• prototype
• rjs

Share Improve this question Follow edited Feb 1, 2016 at 16:53 Sameera R. 4,59222 gold badges3939 silver badges5353 bronze badges asked Mar 10, 2009 at 14:57 JavierJavier 2,53144 gold badges3737 silver badges5757 bronze badges

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 6

I've e up on this many times where I have a conditional item that needs to be acted upon if it exists. Using page.select avoids the Null Value error.

  page.select('#dom_object_id').each do |element|
    element.value = "bar"
  end

I put this in my *.js.rjs file. When the select sends an empty array to each it returns nothing instead of the TypeError you'd get when directly selecting by id when no DOM object with the correct ID is on the page.

I don't think you can from RJS. As a workaround, you can simply call a javascript method from RJS that checks if the element exists.

page << "update_foo('#{my_value}');"

Javascript ..

function update_foo(val)
{
  if( $('foo') != undefined )
  {
    $('foo').value = 'bar';
  } 
}

Edit

Fixed the ruby part..

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