called desc. The process goes something like this: Highlight the area onMouseOver Clear the highlight onMouseOut If the user clicks, hide the area and replace with a

and buttons
	Remove all of the above if the user cancels the operation
	When the Save button is clicked, make an Ajax POST and show that something’s happening
	When the Ajax call comes back, update the page with the new content

Events and Highlighting

The first step is to offer feedback to the user that the item is editable. This is done by shading the background colour when the user mouses over. Of course, the CSS :hover pseudo class is a straightforward way to do this, but for three reasons, I’m using JavaScript to switch class names.

:hover isn’t supported on many elements in Internet Explorer for Windows
	I want to keep control over when the highlight switches off after an update, regardless of mouse position
	If JavaScript isn’t available we don’t want to end up with the CSS suggesting it might be

With this in mind, here’s how editinplace.js starts:

Event.observe(window, 'load', init, false);

function init(){
     makeEditable('desc');
 }

function showAsEditable(obj, clear){
     if (!clear){
          Element.addClassName(obj, 'editable');
     }else{
          Element.removeClassName(obj, 'editable');
     }
 }

The first line attaches an onLoad event to the window, so that the function init() gets called once the page has loaded. In turn, init() sets up all the items on the page that we want to make editable. In this example I’ve just got one, but you can add as many as you like.

The function madeEditable() attaches the mouseover, mouseout and click events to the item we’re making editable. All showAsEditable does is add and remove the class name editable from the object. This uses the particularly cunning methods Element.addClassName() and Element.removeClassName() which enable you to cleanly add and remove effects without affecting any styling the object may otherwise have.

Oh, remember to add a rule for .editable to your style sheet:

.editable{
     color: #000;
     background-color: #ffffd3;
 }

The Switch

As you can see above, when the user clicks on an editable item, a call is made to the function edit(). This is where we switch out the static item for a nice editable textarea. Here’s how that function looks.

function edit(obj){
     Element.hide(obj);

var textarea ='<div id=""' + obj.id + '_editor"">
          <textarea id=""' + obj.id + '_edit"" name=""' + obj.id + '"" rows=""4"" cols=""60"">'
          + obj.innerHTML + '

'; var button = ' OR '; new Insertion.After(obj, textarea+button); Event.observe(obj.id+'_save', 'click', function(){saveChanges(obj)}, false); Event.observe(obj.id+'_cancel', 'click', function(){cleanUp(obj)}, false); } The first thing to do is to hide the object. Prototype comes to the rescue with Element.hide() (and of course, Element.show() too). Following that, we build up the textarea and buttons as a string, and then use Insertion.After() to place our new editor underneath the (now hidden) editable object. The last thing to do before we leave the user to edit is it attach listeners to the Save and Cancel buttons to call either the saveChanges() function, or to cleanUp() after a cancel. In the event of a cancel, we can clean up behind ourselves like so: function cleanUp(obj, keepEditable){ Element.remove(obj.id+'_editor'); Element.show(obj); if (!keepEditable) showAsEditable(obj, true); } Saving the Changes This is where all the Ajax fun occurs. Whilst the previous article introduced Ajax.Updater() for simple Ajax calls, in this case we need a little bit more control over what happens once the response is received. For this purpose, Ajax.Request() is perfect. We can use the onSuccess and onFailure parameters to register functions to handle the response. function saveChanges(obj){ var new_content = escape($F(obj.id+'_edit')); obj.innerHTML = ""Saving...""; cleanUp(obj, true); var success = function(t){editComplete(t, obj);} var failure = function(t){editFailed(t, obj);} var url = 'edit.php'; var pars = 'id=' + obj.id + '&content=' + new_content; var myAjax = new Ajax.Request(url, {method:'post', postBody:pars, onSuccess:success, onFailure:failure}); } function editComplete(t, obj){ obj.innerHTML = t.responseText; showAsEditable(obj, true); } function editFailed(t, obj){ obj.innerHTML = 'Sorry, the update failed.'; cleanUp(obj); } As you can see, we first grab in the contents of the textarea into the variable new_content. We then remove the editor, set the content of the original object to “Saving…” to show that an update is occurring, and make the Ajax POST. If the Ajax fails, editFailed() sets the contents of the object to “Sorry, the update failed.” Admittedly, that’s not a very helpful way to handle the error but I have to limit the scope of this article somewhere. It might be a good idea to stow away the original contents of the object (obj.preUpdate = obj.innerHTML) for later retrieval before setting the content to “Saving…”. No one likes a failure – especially a messy one. If the Ajax call is successful, the server-side script returns the edited content, which we then place back inside the object from editComplete, and tidy up. Meanwhile, back at the server The missing piece of the puzzle is the server-side script for committing the changes to your database. Obviously, any solution I provide here is not going to fit your particular application. For the purposes of getting a functional demo going, here’s what I have in PHP. Not exactly rocket science is it? I’m just catching the content item from the POST and echoing it back. For your application to be useful, however, you’ll need to know exactly which record you should be updating. I’m passing in the ID of my

, which is not a fat lot of use. You can modify saveChanges() to post back whatever information your app needs to know in order to process the update. You should also check the user’s credentials to make sure they have permission to edit whatever it is they’re editing. Basically the same rules apply as with any script in your application. Limitations There are a few bits and bobs that in an ideal world I would tidy up. The first is the error handling, as I’ve already mentioned. The second is that from an idealistic standpoint, I’d rather not be using innerHTML. However, the reality is that it’s presently the most efficient way of making large changes to the document. If you’re serving as XML, remember that you’ll need to replace these with proper DOM nodes. It’s also important to note that it’s quite difficult to make something like this universally accessible. Whenever you start updating large chunks of a document based on user interaction, a lot of non-traditional devices don’t cope well. The benefit of this technique, though, is that if JavaScript is unavailable none of the functionality gets implemented at all – it fails silently. It is for this reason that this shouldn’t be used as a complete replacement for a traditional, universally accessible edit form. It’s a great time-saver for those with the ability to use it, but it’s no replacement. See it in action I’ve put together an example page using the inert PHP script above. That is to say, your edits aren’t committed to a database, so the example is reset when the page is reloaded.",2005,Drew McLellan,drewmclellan,2005-12-23T00:00:00+00:00,https://24ways.org/2005/edit-in-place-with-ajax/,code 324,Debugging CSS with the DOM Inspector,"An Inspector Calls The larger your site and your CSS becomes, the more likely that you will run into bizarre, inexplicable problems. Why does that heading have all that extra padding? Why is my text the wrong colour? Why does my navigation have a large moose dressed as Noel Coward on top of all the links? Perhaps you work in a collaborative environment, where developers and other designers are adding code? In which case, the likelihood of CSS strangeness is higher. You need to debug. You need Firefox’s wise-guy know-it-all, the DOM Inspector. The DOM Inspector knows where everything is in your layout, and more importantly, what causes it to look the way it does. So without further ado, load up any css based site in your copy of Firefox (or Flock for that matter), and launch the DOM Inspector from the Tools menu. The inspector uses two main panels – the left to show the DOM tree of the page, and the right to show you detail: The Inspector will look at whatever site is in the front-most window or tab, but you can also use it without another window. Type in a URL at the top (A), press ‘Inspect’ (B) and a third panel appears at the bottom, with the browser view. I find this layout handier than looking at a window behind the DOM Inspector. Step 1 – find your node! Each element on your page – be it a HTML tag or a piece of text, is called a ‘node’ of the DOM tree. These nodes are all listed in the left hand panel, with any ID or CLASS attribute values next to them. When you first look at a page, you won’t see all those yet. Nested HTML elements (such as a link inside a paragraph) have a reveal triangle next to their name, clicking this takes you one level further down. This can be fine for finding the node you want to look at, but there are easier ways. Say you have a complex rounded box technique that involves 6 nested DIVs? You’d soon get tired of clicking all those triangles to find the element you want to inspect. Click the top left icon © – “Find a node to inspect by clicking on it” and then select the area you want to inspect. Boom! All that drilling down the DOM tree has been done for you! Huzzah! If you’re looking for an element that you know has an ID (such as

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#one { position: relative; z-index: 3; } #two { position: relative; z-index: 1; } #three { position: relative; z-index: 2; } As you can see, the

with the z-index of 3 will appear closest, even though it comes before its siblings in the source order. As these three

s have no defined positioning context in the form of a positioned parent such as a

, their stacking order is defined from the root element . Simple stuff, but these building blocks are the basis on which we can create interesting interfaces (particularly when used in combination with image replacement and transparent PNGs). Brand building Now let’s take three more basic elements, an

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