1

In my grails app, we use jquery. I include jquery on the necessary pages with

<g:javascript library="jquery"/>

If we decide to change javascript libraries, I need to update every page. I know I can include this in the layout, but the library is not needed on every page, so that seems wasteful.

Is there a typical way in grails to specify in one place what the default javascript library should be and then to just include that default one without specifying that it is jquery (or whatever it is) on every page?

Improve this question
1
  • Won't the users already have jQuery cached if they've hit any of your pages that require it? I.e. it wouldn't add too much page weight even if you put it in the main layout (thus, including it on every page). Just a thought. Commented Apr 12, 2012 at 13:26

2 Answers 2

Reset to default
3

Since most browsers heavily cache things like JavaScript libraries, putting the library include into the layout is probably better than putting it in each individual page. The heavy caching that browsers do means that users will only load the library from the server once for your whole site (or at least their browsing session), and by having it be handled in the layout you are drastically reducing your maintenance load (which you alluded to)

In general, your JavaScript libraries should be highly cached, and in many cases it's preferable to pull them from a highly used CDN, like Google's. Your "local" (ie. from your server) library should only get requested if the CDN provider goes down and the browser can't get to their library. (Take a look at the HTML5Boilerplate project for how this is done)

Because of that, I wouldn't worry about the very minimal performance hit that putting the library into the layout page would incur. Even if you don't use a well-used CDN for your library, any browser that people actually use today will only load your JavaScript library once (the first page it gets that includes it) and will simply use it's cached copy for the rest of the pages on your site.

So, in a nutshell, put it in the layout page and don't worry about it. It will only be requested on the first page load, and will come from the cache for all subsequent loads, and your codebase will be DRYer.

Improve this answer
Sign up to request clarification or add additional context in comments.

2 Comments

Is there a way I can tell grails to use the google version of jquery if I wanted to?
The <g:javascript> tag itself doesn't give you any way to specify the particular library version to use, but that tag leverages the resources plugin to do the heavy lifting and that plugin will let you control exactly what gets loaded in.
1

You could also create an external JS file that selectively loads the file(s) you specify. Something like this:

//FILENAME: jselector.js
if ( [conditions] ) {
  var fileref=document.createElement('script');
  fileref.setAttribute("type","text/javascript");
  fileref.setAttribute("src", filename); //reference your Jquery file here
  document.getElementsByTagName("head")[0].appendChild(fileref);
}

Then put a reference to this file (jselector.js) in each of the pages that need it.

<script type="text/javascript" src="jselector.js"></script>

If your jQuery file ever changes, you update this single external JS (jselector.js), and all of the pages will automatically point to the new jQuery.

Improve this answer

3 Comments

The issue with including JS this way is that you incur a slight load-time penalty, since the JS parser has to process this file first before it can load in the extra scripts, and you have one more thing that can cause odd behavior due to unexpected caching. For something as core as the jQuery library, I would say that one is better off including it the "normal" way.
I aqree with you. That's why I mentioned it in my comment above. But since that doesn't directly answer the asker's question, I wanted to provide an answer in addition to my opinion that using it in all page layouts wouldn't make much difference. But I rely on the caching approach in my apps.
@Marc, thanks for your reply. You answered the question, but it seems like my thought that putting it in the layout was a bad idea is actually not correct.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.