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Using JavaScript in themes the right way

From: WordPress 3: Creating and Editing Custom Themes

Video: Using JavaScript in themes the right way

I would like to talk a little bit about using JavaScript within a WordPress theme. So when you use JavaScript, you link out to JavaScript files from somewhere within your website. I have our whole theme folder opened up as a project here in TextMate. In the header.php file, we could link out the scripts right from within here. I could do something like this. Script src = js/test.js, close that script tag, and there we go.

Using JavaScript in themes the right way

I would like to talk a little bit about using JavaScript within a WordPress theme. So when you use JavaScript, you link out to JavaScript files from somewhere within your website. I have our whole theme folder opened up as a project here in TextMate. In the header.php file, we could link out the scripts right from within here. I could do something like this. Script src = js/test.js, close that script tag, and there we go.

We have some JavaScript that's going to be loaded and activated on this page. You might see it in the head section. You might often see it in the footer. It's often recommended that for speed purposes scripts can be loaded just before the closing body tag down here so they don't interfere with the loading of the page. That's pretty common. So that's one way. It's absolutely going to work in your WordPress theme. There is no reason why you can't do it that way. But there is an important concept here, and if you are working with JavaScript these days, there is a really high chance that you are working with one of the popular JavaScript Libraries, which is jQuery, MooTools, Prototype, Dojo, Yahoo! User Interface, there is a bunch of these ones.

jQuery is really popular one. So we are going to be loading up the jQuery library first and then our custom script. So it depends on that library being loaded first. So how do we do that? Well, in the blank theme that we started with there is this function.php file, and we only made one little alternation to it when we added our menus, but all the rest of this code came from that blank theme. We haven't touched it very much. I want to focus on this section right here. There is a few things going on right here.

First thing is it does a test and it says, if and then an exclamation point is_admin. It's saying if it's not the admin area, then do this code in between here. And there's three functions that are running. One of them says deregister_script, wp_deregister_script jquery, and wp_register_script jquery, and then enqueue_script jquery. So what its doing is it's saying that jQuery has already been a registered script, whatever that is, and then so I want to deregister it and then reregister it and then enqueue it.

So if we were to remove these two lines right here-- Let me just comment them out. This is still going to work. It's still going to enqueue JavaScript in our theme. Now I want to save that, I want to reload this homepage, and I want to take a look at the source. I'm in Safari here, so I'm going to press Command+Option+U and look at the source code for this. And you can see right at this line here, it's loading the JavaScript Library and you'll notice the file path. It's loading it from this wp_includes folder right within our JavaScript installation.

Now, if I close that out, come back over here, and uncomment these two lines, and in TextMate, I can highlight multiple lines and comment or uncomment things with Command+/. Now it's deregistering and reregistering with this URL. Now, that URL points to a version of jQuery that lives out on Google Servers. Now, the reason you might want to do that is because, chances are Google Servers are a lot faster than yours, lot more reliable than yours, and if another page uses this, which is very common, it's going to come out of your browser's cache and still having to re-download it again.

It's just a faster way to use a library like Google. I'm going to save that. Refresh the page and let's peek at the source code. Again, that gets rendered out and instead of-- it's still loading jQuery right here, but it's loading it from that Google location instead. So that's what's going on there. But it's not doing it for the admin area, which also has some JavaScript effects in there, so we don't want to affect the backend. If we choose to use a more up-to- date version of jQuery, let's say, than WordPress ships with, then we won't interfere with any of that backend stuff.

Now, you notice how that worked even if these two lines were gone, that still worked, because jQuery is one of the scripts that comes with WordPress. Now, there's a number of other ones that come with it. If we wanted to use Prototype, we could just put the word prototype in there, reload the page over here, view the source. You can see that the Prototype Library is being linked to it here. It also ships with WordPress. So what are all of your different options, what are all the different scripts that ship with WordPress? There is this URL right here that comes right from WordPress.org itself and it's just a big list of all the scripts that ship with WordPress.

So that's pretty cool. Now, you aren't necessarily limited to scripts that ship with WordPress, because like you said, we wrote over the jQuery Library that came with it. We can register our own scripts if we want to. And that's a different function. It looks like this. wp_register_script. And we have to give it a name. We'll call it myscript. And we've got to give it a location. Now, we're going to put it in our theme. We're going to say this JavaScript is dependent on this theme. We'll just call it test.js.

So we have a new JavaScript file in our theme, test.js. Now, we need to tell it the location that script exists. So we will go get_bloginfo, which has a bunch of information on it about our blog, including where our template directory is, and we'll add to that /js/test.js Now it's registered, so my script has a value of where it lives and what file it's referencing.

We need to enqueue it as well. wp_enqueue, and we'll just say myscript. So if we save that and we reload our homepage over here and view source again, we'll be able to see that we're also additionally queuing up this script. And you will see one little weird thing here. It's appending on this version number to the end of it. That's the version of WordPress that's currently running. That automatically happens because WordPress may, in an update, adjust the version of the JavaScript file that it ships with and it just wants to make sure that it doesn't pull an old version out of cache in case there is a dependency there.

So that's just why that happens. It's not going to affect your JavaScript file in any way. So why is this all happening in the functions.php file? It's only just to keep it clean really. We could put the same code into the header.php file, assuming we do it before the wp_head call. So you see all that-- we keep viewing source over here and taking a look at this kind of big block of code that gets pumped out here? We keep having to view source to see that, because in our header.php file, it's just this one line.

It's just this wp_head. So all the stuff that gets enqueued, just gets spit out at this one little line here and it keeps our header.php file clean. You can see there is already enough stuff in here. So it's just kind of a way to keep ourselves organized and clean. It's the fact that we can enqueue these scripts back here. Now, the most important part that we haven't mentioned yet about enqueuing scripts is that it's just the courteous thing to do. It tells WordPress that we are indeed using jQuery.

Now, if another script comes along and also needs jQuery, WordPress already knows that you have jQuery registered and won't overwrite you. It won't load another copy of jQuery, which will almost certainly cause problems. There is a popular plug-in called WP-Pulse. It's great. If you want to add Pulse to your site, just load up this plug-in, put it in there, and you can add a Pulse to your sidebar in your widgetized area. It also ships with jQuery and loads up jQuery. Now, if we were to go into our header.php file, just put a script tag right in here, have that link out to jQuery somewhere, WordPress doesn't know about that and it's going to load up when we use WP-Pulse another copy of jQuery.

We have two copies of jQuery being loaded. There is going to be conflicts. There is going to be problems. And even if there isn't, it's loading that copy twice and that's a waste of bandwidth and all that. So it's just the courteous, smart thing to do to use wp and enqueue script to load up your jQuery files, or any JavaScript files really.

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This video is part of

Image for WordPress 3: Creating and Editing Custom Themes
WordPress 3: Creating and Editing Custom Themes

40 video lessons · 51836 viewers

Chris Coyier
Author

 
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  1. 6m 44s
    1. Welcome
      1m 19s
    2. Using the exercise files
      5m 25s
  2. 40m 42s
    1. Reviewing the client spec and deciding on WordPress
      6m 50s
    2. Reviewing assets and resources and creating a mood board
      8m 41s
    3. Building a home page mockup
      11m 26s
    4. Finishing the home page
      12m 27s
    5. Planning the rest of the site
      1m 18s
  3. 1h 8m
    1. Starting with a base project
      3m 6s
    2. Writing HTML code for the home page
      12m 7s
    3. Starting the CSS: Creating the header and basic style structure
      11m 28s
    4. Styling the Navigation panel
      10m 59s
    5. Styling the sidebar
      7m 55s
    6. Styling the home page, pt. 1
      8m 20s
    7. Styling the home page, pt. 2
      8m 17s
    8. Finishing the CSS
      3m 14s
    9. Moving on: One page is enough
      2m 43s
  4. 1h 56m
    1. Setting up WordPress and MAMP on a Mac
      6m 7s
    2. Setting up WordPress and WAMP on a Windows computer
      5m 38s
    3. Modifying important settings
      6m 26s
    4. Starting with a blank theme template
      4m 35s
    5. Introducing template file structure
      4m 55s
    6. Breaking up the HTML
      9m 53s
    7. Building the sidebar
      3m 54s
    8. Building the navigation
      7m 20s
    9. Showing one recent post
      4m 1s
    10. Fetching external content
      8m 23s
    11. Creating a custom home page
      3m 30s
    12. Introducing custom fields
      5m 23s
    13. Creating custom product pages
      9m 52s
    14. Creating custom category pages
      15m 39s
    15. Creating the blog home page
      5m 39s
    16. Creating a single blog entry page
      4m 15s
    17. Implementing comments
      5m 57s
    18. Finishing the home page
      4m 45s
  5. 34m 17s
    1. Will this work with WordPress?
      3m 10s
    2. Using JavaScript in themes the right way
      8m 35s
    3. Implementing something fun with JavaScript
      7m 53s
    4. Introducing plug-ins
      6m 31s
    5. Setting up security
      8m 8s
  6. 2m 7s
    1. Goodbye
      2m 7s

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