{"rowid": 124, "title": "Writing Responsible JavaScript", "contents": "Without a doubt, JavaScript has been making something of a comeback in the last year. If you\u2019re involved in client-side development in any way at all, chances are that you\u2019re finding yourself writing more JavaScript now than you have in a long time.\n\nIf you learned most of your JavaScript back when DHTML was all the rage and before DOM Scripting was in vogue, there have been some big shifts in the way scripts are written. Most of these are in the way event handlers are assigned and functions declared. Both of these changes are driven by the desire to write scripts that are responsible page citizens, both in not tying behaviour to content and in taking care not to conflict with other scripts. I thought it may be useful to look at some of these more responsible approaches to learn how to best write scripts that are independent of the page content and are safely portable between different applications.\n\nEvent Handling\n\nBack in the heady days of Web 1.0, if you wanted to have an object on the page react to something like a click, you would simply go ahead and attach an onclick attribute. This was easy and understandable, but much like the font tag or the style attribute, it has the downside of mixing behaviour or presentation in with our content. As we\u2019re learned with CSS, there are big benefits in keeping those layers separate. Hey, if it works for CSS, it should work for JavaScript too.\n\nJust like with CSS, instead of adding an attribute to our element within the document, the more responsible way to do that is to look for the item from your script (like CSS does with a selector) and then assign the behaviour to it. To give an example, take this oldskool onclick use case:\n\nPlay the animation\n\nThis could be rewritten by removing the onclick attribute, and instead doing the following from within your JavaScript.\n\ndocument.getElementById('anim-link').onclick = playAnimation;\n\nIt\u2019s all in the timing\n\nOf course, it\u2019s never quite that easy. To be able to attach that onclick, the element you\u2019re targeting has to exist in the page, and the page has to have finished loading for the DOM to be available. This is where the onload event is handy, as it fires once everything has finished loading. Common practise is to have a function called something like init() (short for initialise) that sets up all these event handlers as soon as the page is ready.\n\nBack in the day we would have used the onload attibute on the element to do this, but of course what we really want is:\n\nwindow.onload = init;\n\nAs an interesting side note, we\u2019re using init here rather than init() so that the function is assigned to the event. If we used the parentheses, the init function would have been run at that moment, and the result of running the function (rather than the function itself) would be assigned to the event. Subtle, but important.\n\nAs is becoming apparent, nothing is ever simple, and we can\u2019t just go around assigning our initialisation function to window.onload. What if we\u2019re using other scripts in the page that might also want to listen out for that event? Whichever script got there last would overwrite everything that came before it. To manage this, we need a script that checks for any existing event handlers, and adds the new handler to it. Most of the JavaScript libraries have their own systems for doing this. If you\u2019re not using a library, Simon Willison has a good stand-alone example\n\nfunction addLoadEvent(func) {\n\tvar oldonload = window.onload;\n\tif (typeof window.onload != 'function') {\n\t\twindow.onload = func;\n\t} else {\n\t\twindow.onload = function() {\n\t\t\tif (oldonload) {\n\t\t\t\toldonload();\n\t\t\t}\n\t\t\tfunc();\n\t\t}\n\t}\n}\n\nObviously this is just a toe in the events model\u2019s complex waters. Some good further reading is PPK\u2019s Introduction to Events.\n\nCarving out your own space\n\nAnother problem that rears its ugly head when combining multiple scripts on a single page is that of making sure that the scripts don\u2019t conflict. One big part of that is ensuring that no two scripts are trying to create functions or variables with the same names. Reusing a name in JavaScript just over-writes whatever was there before it.\n\nWhen you create a function in JavaScript, you\u2019ll be familiar with doing something like this.\n\nfunction foo() {\n\t... goodness ...\n}\n\nThis is actually just creating a variable called foo and assigning a function to it. It\u2019s essentially the same as the following.\n\nvar foo = function() {\n\t... goodness ...\n}\n\nThis name foo is by default created in what\u2019s known as the \u2018global namespace\u2019 \u2013 the general pool of variables within the page. You can quickly see that if two scripts use foo as a name, they will conflict because they\u2019re both creating those variables in the global namespace.\n\nA good solution to this problem is to add just one name into the global namespace, make that one item either a function or an object, and then add everything else you need inside that. This takes advantage of JavaScript\u2019s variable scoping to contain you mess and stop it interfering with anyone else.\n\nCreating An Object\n\nSay I was wanting to write a bunch of functions specifically for using on a site called \u2018Foo Online\u2019. I\u2019d want to create my own object with a name I think is likely to be unique to me.\n\nvar FOOONLINE = {};\n\nWe can then start assigning functions are variables to it like so:\n\nFOOONLINE.message = 'Merry Christmas!';\nFOOONLINE.showMessage = function() {\n\talert(this.message);\n};\n\nCalling FOOONLINE.showMessage() in this example would alert out our seasonal greeting. The exact same thing could also be expressed in the following way, using the object literal syntax.\n\nvar FOOONLINE = {\n\tmessage: 'Merry Christmas!',\n\tshowMessage: function() {\n\t\talert(this.message);\n\t}\n};\n\nCreating A Function to Create An Object\n\nWe can extend this idea bit further by using a function that we run in place to return an object. The end result is the same, but this time we can use closures to give us something like private methods and properties of our object.\n\nvar FOOONLINE = function(){\n\tvar message = 'Merry Christmas!';\n\treturn {\n\t\tshowMessage: function(){\n\t\t\talert(message);\n\t\t}\n\t}\n}();\n\nThere are two important things to note here. The first is the parentheses at the end of line 10. Just as we saw earlier, this runs the function in place and causes its result to be assigned. In this case the result of our function is the object that is returned at line 4.\n\nThe second important thing to note is the use of the var keyword on line 2. This ensures that the message variable is created inside the scope of the function and not in the global namespace. Because of the way closure works (which if you\u2019re not familiar with, just suspend your disbelief for a moment) that message variable is visible to everything inside the function but not outside. Trying to read FOOONLINE.message from the page would return undefined.\n\nThis is useful for simulating the concept of private class methods and properties that exist in other programming languages. I like to take the approach of making everything private unless I know it\u2019s going to be needed from outside, as it makes the interface into your code a lot clearer for someone else to read. \n\nAll Change, Please\n\nSo that was just a whistle-stop tour of a couple of the bigger changes that can help to make your scripts better page citizens. I hope it makes useful Sunday reading, but obviously this is only the tip of the iceberg when it comes to designing modular, reusable code.\n\nFor some, this is all familiar ground already. If that\u2019s the case, I encourage you to perhaps submit a comment with any useful resources you\u2019ve found that might help others get up to speed. Ultimately it\u2019s in all of our interests to make sure that all our JavaScript interoperates well \u2013 share your tips.", "year": "2006", "author": "Drew McLellan", "author_slug": "drewmclellan", "published": "2006-12-10T00:00:00+00:00", "url": "https://24ways.org/2006/writing-responsible-javascript/", "topic": "code"}
{"rowid": 144, "title": "The Mobile Web, Simplified", "contents": "A note from the editors: although eye-opening in 2006, this article is no longer relevant to today\u2019s mobile web.\n \n \n \n Considering a foray into mobile web development? Following are four things you need to know before making the leap.\n\n1. 4 billion mobile subscribers expected by 2010\n\nFancy that. Coupled with the UN prediction of 6.8 billion humans by 2010, 4 billion mobile subscribers (source) is an astounding 59% of the planet. Just how many of those subscribers will have data plans and web-enabled phones is still in question, but inevitably this all means one thing for you and me: A ton of potential eyes to view our web content on a mobile device.\n\n2. Context is king\n\nYour content is of little value to users if it ignores the context in which it is viewed. Consider how you access data on your mobile device. You might be holding a bottle of water or gripping a handle on the subway/tube. You\u2019re probably seeking specific data such as directions or show times, rather than the plethora of data at your disposal via a desktop PC.\n\nThe mobile web, a phrase often used to indicate \u201caccessing the web on a mobile device\u201d, is very much a context-, content-, and component-specific environment. Expressed in terms of your potential target audience, access to web content on a mobile device is largely influenced by surrounding circumstances and conditions, information relevant to being mobile, and the feature set of the device being used. Ask yourself, What is relevant to my users and the tasks, problems, and needs they may encounter while being mobile? Answer that question and you\u2019ll be off to a great start.\n\n3. WAP 2.0 is an XHTML environment\n\nIn a nutshell, here are a few fundamental tenets of mobile internet technology:\n\n\n\tWireless Application Protocol (WAP) is the protocol for enabling mobile access to internet content.\n\tWireless Markup Language (WML) was the language of choice for WAP 1.0.\n\tNearly all devices sold today are WAP 2.0 devices.\n\tWith the introduction of WAP 2.0, XHTML Mobile Profile (XHTML-MP) became the preferred markup language.\n\tXHTML-MP will be familiar to anyone experienced with XHTML Transitional or Strict.\n\n\nSummary? The mobile web is rapidly becoming an XHTML environment, and thus you and I can apply our existing \u201cdesktop web\u201d skills to understand how to develop content for it. With WML on the decline, the learning curve is much smaller today than it was several years ago. I\u2019m generalizing things gratuitously, but the point remains: Get off yo\u2019 lazy butt and begin to take mobile seriously.\n\nI\u2019ll even pass you a few tips for getting started. First, the DOCTYPE for XHTML-MP is as follows:\n\n\n\nAs for MIME type, Open Mobile Alliance (OMA) specifies using the MIME type application/vnd.wap.xhtml+xml, but ultimately you need to ensure the server delivering your mobile content is configured properly for the MIME type you choose to use, as there are other options (see Setting up WAP Servers).\n\nOnce you\u2019ve made it to the body, the XHTML-MP markup is not unlike what you\u2019re already used to. A few resources worth skimming:\n\n\n\tDevelopers Home XHTML-MP Tutorial \u2013 An impressively replete resource for all things XHTML-MP\n\tXHTML-MP Tags List \u2013 A complete list of XHTML-MP elements and accompanying attributes\n\n\nAnd last but certainly not least, CSS. There exists WAP CSS, which is essentially a subset of CSS2 with WAP-specific extensions. For all intents and purposes, much of the CSS you\u2019re already comfortable using will be transferrable to mobile. As for including CSS in your pages, your options are the same as for desktop sites: external, embedded, and inline. Some experts will argue embedded or inline over external in favor of reducing the number of HTTP connections per page request, yet many popular mobilized sites and apps employ external linking without issue.\n\nStocking stuffers: Flickr Mobile, Fandango Mobile, and Popurls Mobile. A few sites with whom you can do the View Source song and dance for further study.\n\n4. \u201cCell phone\u201d is so DynaTAC\n\nIf you\u2019re a U.S. resident, listen up: You must rid your vocabulary of the term \u201ccell phone\u201d. We\u2019re one of the few economies on the planet to refer to a mobile phone accordingly. If you care to find yourself in any of the worthwhile mobile development circles, begin using terms more widely accepted: \u201cmobile\u201d or \u201cmobile phone\u201d or \u201chandset\u201d or \u201chandy\u201d. If you\u2019re not sure which, go for \u201cmobile\u201d. Such as, \u201cYo dog, check out my new mobile.\u201d\n\nMore importantly, however, is overcoming the mentality that access to the mobile web can be done only with a phone. Instead, \u201cdevice\u201d encourages us to think phone, handheld computer, watch, Nintendo DS, car, you name it.\n\nSimple enough?", "year": "2006", "author": "Cameron Moll", "author_slug": "cameronmoll", "published": "2006-12-19T00:00:00+00:00", "url": "https://24ways.org/2006/the-mobile-web-simplified/", "topic": "ux"}
{"rowid": 132, "title": "Tasty Text Trimmer", "contents": "In most cases, when designing a user interface it\u2019s best to make a decision about how data is best displayed and stick with it. Failing to make a decision ultimately leads to too many user options, which in turn can be taxing on the poor old user. \n\nUnder some circumstances, however, it\u2019s good to give the user freedom in customising their workspace. One good example of this is the \u2018Article Length\u2019 tool in Apple\u2019s Safari RSS reader. Sliding a slider left of right dynamically changes the length of each article shown. It\u2019s that kind of awesomey magic stuff that\u2019s enough to keep you from sleeping. Let\u2019s build one.\n\nThe Setup\n\nLet\u2019s take a page that has lots of long text items, a bit like a news page or like Safari\u2019s RSS items view. If we were to attach a class name to each element we wanted to resize, that would give us something to hook onto from the JavaScript. \n\nExample 1: The basic page.\n\nAs you can see, I\u2019ve wrapped my items in a DIV and added a class name of chunk to them. It\u2019s these chunks that we\u2019ll be finding with the JavaScript. Speaking of which \u2026\n\nOur Core Functions\n\nThere are two main tasks that need performing in our script. The first is to find the chunks we\u2019re going to be resizing and store their original contents away somewhere safe. We\u2019ll need this so that if we trim the text down we\u2019ll know what it was if the user decides they want it back again. We\u2019ll call this loadChunks. \n\nvar loadChunks = function(){\n\tvar everything = document.getElementsByTagName('*');\n\tvar i, l;\n\tchunks\t= [];\n\tfor (i=0, l=everything.length; i -1){\n\t\t\tchunks.push({\n\t\t\t\tref: everything[i],\n\t\t\t\toriginal: everything[i].innerHTML\n\t\t\t});\n\t\t}\n\t}\n};\n\nThe variable chunks is stored outside of this function so that we can access it from our next core function, which is doTrim.\n\nvar doTrim = function(interval) {\n\tif (!chunks) loadChunks();\n\tvar i, l;\n\tfor (i=0, l=chunks.length; i\n\t
\n\n\t\n\t\t 1485 Laperri\u00e8re Avenue \n\t\t Ottawa ON K1Z 7S8 \n\t\tCanada\n\t\n\n\t\n\t\tPhone/Fax: Work: 61 2 9365 5007\n\t\tEmail: info@webdirections.org\n\t\n\n\nWe\u2019ll be using a variation on the now well established \u201csliding doors\u201d technique (if you create a CSS technique, remember it\u2019s very important to give it a memorable name or acronym, and bonus points if you get your name in there!) by Douglas Bowman, enhanced by Scott Schiller (see http://www.schillmania.com/projects/dialog/,) which will give us a design which looks like this\n\n\n\nThe technique, in a nutshell, uses background images on four elements, two at the top, and two at the bottom, to add each rounded corner.\n\nWe are going to make this design \u201cfluid\u201d in the sense that it grows and shrinks in proportion with the size of the font that the text of the element is displayed with. This is sometimes referred to as an \u201cem driven design\u201d (we\u2019ll see why in a moment).\n\nTo see how this works in practice, here\u2019s the same design with the text \u201czoomed\u201d up in size\n\n\n\nand the same design again, when we zoom the text size down\n\n\n\nBy the way, the hCard image comes from Chris Messina, and you can download it and other microformat icons from the microformats wiki.\n\nNow, with CSS3, this whole task would be considerably easier, because we can add multiple background images to an element, and border images for each edge of an element. Safari, version 1.3 up, actually supports multiple background images, but sadly, it\u2019s not supported in Firefox 1.5, or even Firefox 2.0 (let\u2019s not mention IE7 eh?). So it\u2019s probably too little supported to use now. So instead we\u2019ll use a technique that only involves CSS2, and works in pretty much any browser.\n\nVery often, developers add div or span elements as containers for these background images, and in fact, if you visit Scott Shiller\u2019s site, that\u2019s what he has done there. But if at all possible we shouldn\u2019t be adding any HTML simply for presentational purposes, even if the presentation is done via CSS. What we can do is to use the HTML we have already, as much as is possible, to add the style we want. This can take some creative thinking, but once you get the hang of this approach it becomes a more natural way of using HTML compared with simply adding divs and spans at will as hooks for style. Of course, this technique isn\u2019t always simple, and in fact sometimes simply not possible, requiring us to add just a little HTML to provide the \u201chooks\u201d for CSS.\n\nLet\u2019s go to work\n\nThe first step is to add a background image to the whole vCard element.\n\n\n\nWe make this wide enough (for example 1000 or more pixels) and tall enough that no matter how large the content of the vCard grows, it will never overflow this area. We can\u2019t simply repeat the image, because the top left corner will show when the image repeats.\n\nWe add this as the background image of the vCard element using CSS.\n\nWhile we are at it, let\u2019s give the text a sans-serif font, some color so that it will be visible, and stop the image repeating.\n\n.vcard {\n\tbackground-image: url(images/vcardfill.png);\n\tbackground-repeat: no-repeat;\n\tcolor: #666;\n\tfont-family: \"Lucida Grande\", Verdana, Helvetica, Arial, sans-serif;\n}\n\nWhich in a browser, will look something like this.\n\n\n\nNext step we need to add the top right hand corner of the hCard. In keeping with our aim of not adding HTML simply for styling purposes, we want to use the existing structure of the page where possible. Here, we\u2019ll use the paragraph of class fn and org, which is the first child element of the vcard element.\n\n
Web Directions Conference Pty Ltd
\n\nHere\u2019s our CSS for this element\n\n.fn {\n\tbackground-image: url(images/topright.png);\n\tbackground-repeat: no-repeat;\n\tbackground-position: top right;\n\tpadding-top: 2em;\n\tfont-weight: bold;\n\tfont-size: 1.1em;\n}\n\nAgain, we don\u2019t want it to repeat, but this time, we\u2019ve specified a background position for the image. This will make the background image start from the top, but its right edge will be located at the right edge of the element. I also made the font size a little bigger, and the weight bold, to differentiate it from the rest of the text in the hCard.\n\nHere\u2019s the image we are adding as the background to this element.\n\n\n\nSo, putting these two CSS statements together we get\n\n\n\nWe specified a padding-top of 2em to give some space between the content of the fn element and the edge of the fn element. Otherwise the top of the hCard image would be hard against the border. To see this in action, just remove the padding-top: 2em; declaration and preview in a browser.\n\nSo, with just two statements, we are well under way. We\u2019ve not even had to add any HTML so far. Let\u2019s turn to the bottom of the element, and add the bottom border (well, the background image which will serve as that border).\n\nNow, which element are we going to use to add this background image to?\n\nOK, here I have to admit to a little, teensie bit of cheating. If you look at the HTML of the hCard, I\u2019ve grouped the email and telephone properties into a div, with a class of telecommunications. This grouping is not strictly requred for our hCard.\n\n
\n\nNow, I chose that class name because that is what the vCard specification calls this group of properties. And typically, I do tend to group together related elements using divs when I mark up content. I find it makes the page structure more logical and readable. But strictly speaking, this isn\u2019t necessary, so you may consider it cheating. But my lesson in this would be, if you are going to add markup, try to make it as meaningful as possible.\n\nAs you have probably guessed by now, we are going to add one part of the bottom border image to this element. We\u2019re going to add this image as the background-image.\n\n\n\nAgain, it will be a very wide image, like the top left one, so that no matter how wide the element might get, the background image will still be wide enough. Now, we\u2019ll need to make this image sit in the bottom left of the element we attach it to, so we use a backgound position of left bottom (we put the horizontal position before the vertical). Here\u2019s our CSS statement for this\n\n.telecommunications {\n\tbackground-image: url(images/bottom-left.png);\n\tbackground-repeat: no-repeat;\n\tbackground-position: left bottom;\n\tmargin-bottom: 2em;\n}\n\nAnd that will look like this\n\n\n\nNot quite there, but well on the way. Time for the final piece in the puzzle.\n\nOK, I admit, I might have cheated just a little bit more in this step. But like the previous step, all valid, and (hopefully) quite justifiable markup. If we look at the HTML again, you\u2019ll find that our email address is marked up like this\n\n
![\"download](\"images/vcard-add.png\")
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