{"rowid": 316, "title": "Have Your DOM and Script It Too", "contents": "When working with the XMLHttpRequest object it appears you can only go one of three ways: \n\n\n\tYou can stay true to the colorful moniker du jour and stick strictly to the responseXML property\n\tYou can play with proprietary \u2013 yet widely supported \u2013 fire and inject the value of responseText property into the innerHTML of an element of your choosing\n\tOr you can be eval() and parse JSON or arbitrary JavaScript delivered via responseText\n\n\nBut did you know that there\u2019s a fourth option giving you the best of the latter two worlds? Mint uses this unmentioned approach to grab fresh HTML and run arbitrary JavaScript simultaneously. Without relying on eval(). \u201cBut wait-\u201d, you might say, \u201cwhen would I need to do this?\u201d Besides the example below this technique is handy for things like tab groups that need initialization onload but miss the main onload event handler by a mile thanks to asynchronous scripting.\n\nConsider the problem\n\nOriginally Mint used option 2 to refresh or load new tabs into individual Pepper panes without requiring a full roundtrip to the server. This was all well and good until I introduced the new Client Mode which when enabled allows anyone to view a Mint installation without being logged in. If voyeurs are afoot as Client Mode is disabled, the next time they refresh a pane the entire login page is inserted into the current document. That\u2019s not very helpful so I needed a way to redirect the current document to the login page.\n\n\n\nEnter the solution\n\nWouldn\u2019t it be cool if browsers interpreted the contents of script tags crammed into innerHTML? Sure, but unfortunately, that just wasn\u2019t meant to be. However like the body element, image elements have an onload event handler. When the image has fully loaded the handler runs the code applied to it. See where I\u2019m going with this?\n\nBy tacking a tiny image (think single pixel, transparent spacer gif \u2013 shudder) onto the end of the HTML returned by our Ajax call, we can smuggle our arbitrary JavaScript into the existing document. The image is added to the DOM, and our stowaway can go to town.\n\n

This is the results of our Ajax call.

\n \"\"\n\nPlease be neat\n\nSo we\u2019ve just jammed some meaningless cruft into our DOM. If our script does anything with images this addition could have some unexpected side effects. (Remember The Fly?) So in order to save that poor, unsuspecting element whose innerHTML we just swapped out from sharing Jeff Goldblum\u2019s terrible fate we should tidy up after ourselves. And by using the removeChild method we do just that.\n\n

This is the results of our Ajax call.

\n \"\"", "year": "2005", "author": "Shaun Inman", "author_slug": "shauninman", "published": "2005-12-24T00:00:00+00:00", "url": "https://24ways.org/2005/have-your-dom-and-script-it-too/", "topic": "code"} {"rowid": 315, "title": "Edit-in-Place with Ajax", "contents": "Back on day one we looked at using the Prototype library to take all the hard work out of making a simple Ajax call. While that was fun and all, it didn\u2019t go that far towards implementing something really practical. We dipped our toes in, but haven\u2019t learned to swim yet.\n\nSo here is swimming lesson number one. Anyone who\u2019s used Flickr to publish their photos will be familiar with the edit-in-place system used for quickly amending titles and descriptions on photographs. Hovering over an item turns its background yellow to indicate it is editable. A simple click loads the text into an edit box, right there on the page.\n\n\n\nPrototype includes all sorts of useful methods to help reproduce something like this for our own projects. As well as the simple Ajax GETs we learned how to do last time, we can also do POSTs (which we\u2019ll need here) and a whole bunch of manipulations to the user interface \u2013 all through simple library calls. Here\u2019s what we\u2019re building, so let\u2019s do it.\n\nGetting Started\n\nThere are two major components to this process; the user interface manipulation and the Ajax call itself. Our set-up is much the same as last time (you may wish to read the first article if you\u2019ve not already done so). We have a basic HTML page which links in the prototype.js file and our own editinplace.js. Here\u2019s what Santa dropped down my chimney: \n\n\n \n \n \n Edit-in-Place with Ajax\n \n \n \n \n\n

Edit-in-place

\n

Dashing through the snow on a one horse open sleigh.

\n \n \n\nSo that\u2019s our page. The editable item is going to be the

called desc. The process goes something like this:\n\n\n\tHighlight the area onMouseOver\n\tClear the highlight onMouseOut\n\tIf the user clicks, hide the area and replace with a ';\n\n var button = ' OR \n ';\n\n new Insertion.After(obj, textarea+button);\n\n Event.observe(obj.id+'_save', 'click', function(){saveChanges(obj)}, false);\n Event.observe(obj.id+'_cancel', 'click', function(){cleanUp(obj)}, false);\n\n }\n\nThe 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.\n\nThe 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.\n\nIn the event of a cancel, we can clean up behind ourselves like so:\n\nfunction cleanUp(obj, keepEditable){\n Element.remove(obj.id+'_editor');\n Element.show(obj);\n if (!keepEditable) showAsEditable(obj, true);\n }\n\nSaving the Changes\n\nThis 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.\n\nfunction saveChanges(obj){\n var new_content = escape($F(obj.id+'_edit'));\n\n obj.innerHTML = \"Saving...\";\n cleanUp(obj, true);\n\n var success = function(t){editComplete(t, obj);}\n var failure = function(t){editFailed(t, obj);}\n\n var url = 'edit.php';\n var pars = 'id=' + obj.id + '&content=' + new_content;\n var myAjax = new Ajax.Request(url, {method:'post',\n postBody:pars, onSuccess:success, onFailure:failure});\n }\n\n function editComplete(t, obj){\n obj.innerHTML = t.responseText;\n showAsEditable(obj, true);\n }\n\n function editFailed(t, obj){\n obj.innerHTML = 'Sorry, the update failed.';\n cleanUp(obj);\n }\n\nAs 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 \u201cSaving\u2026\u201d to show that an update is occurring, and make the Ajax POST.\n\nIf the Ajax fails, editFailed() sets the contents of the object to \u201cSorry, the update failed.\u201d Admittedly, that\u2019s 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 \u201cSaving\u2026\u201d. No one likes a failure \u2013 especially a messy one.\n\nIf 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.\n\nMeanwhile, back at the server\n\nThe 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\u2019s what I have in PHP.\n\n\n\nNot exactly rocket science is it? I\u2019m just catching the content item from the POST and echoing it back. For your application to be useful, however, you\u2019ll need to know exactly which record you should be updating. I\u2019m 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.\n\nYou should also check the user\u2019s credentials to make sure they have permission to edit whatever it is they\u2019re editing. Basically the same rules apply as with any script in your application.\n\nLimitations\n\nThere are a few bits and bobs that in an ideal world I would tidy up. The first is the error handling, as I\u2019ve already mentioned. The second is that from an idealistic standpoint, I\u2019d rather not be using innerHTML. However, the reality is that it\u2019s presently the most efficient way of making large changes to the document. If you\u2019re serving as XML, remember that you\u2019ll need to replace these with proper DOM nodes.\n\nIt\u2019s also important to note that it\u2019s 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\u2019t cope well. The benefit of this technique, though, is that if JavaScript is unavailable none of the functionality gets implemented at all \u2013 it fails silently. It is for this reason that this shouldn\u2019t be used as a complete replacement for a traditional, universally accessible edit form. It\u2019s a great time-saver for those with the ability to use it, but it\u2019s no replacement.\n\nSee it in action\n\nI\u2019ve put together an example page using the inert PHP script above. That is to say, your edits aren\u2019t committed to a database, so the example is reset when the page is reloaded.", "year": "2005", "author": "Drew McLellan", "author_slug": "drewmclellan", "published": "2005-12-23T00:00:00+00:00", "url": "https://24ways.org/2005/edit-in-place-with-ajax/", "topic": "code"} {"rowid": 324, "title": "Debugging CSS with the DOM Inspector", "contents": "An Inspector Calls\n\nThe 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? \n\nPerhaps you work in a collaborative environment, where developers and other designers are adding code? In which case, the likelihood of CSS strangeness is higher.\n\nYou need to debug. You need Firefox\u2019s wise-guy know-it-all, the DOM Inspector. \n\nThe 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.\n\nThe inspector uses two main panels \u2013 the left to show the DOM tree of the page, and the right to show you detail:\n\n\n\nThe 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 \u2018Inspect\u2019 (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.\n\nStep 1 \u2013 find your node!\n\nEach element on your page \u2013 be it a HTML tag or a piece of text, is called a \u2018node\u2019 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\u2019t 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. \n\nThis 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\u2019d soon get tired of clicking all those triangles to find the element you want to inspect. Click the top left icon \u00a9 \u2013 \u201cFind a node to inspect by clicking on it\u201d and then select the area you want to inspect. Boom! All that drilling down the DOM tree has been done for you! Huzzah!\n\nIf you\u2019re looking for an element that you know has an ID (such as