{"rowid": 46, "title": "Responsive Enhancement", "contents": "24 ways has been going strong for ten years. That\u2019s an aeon in internet timescales. Just think of all the changes we\u2019ve seen in that time: the rise of Ajax, the explosion of mobile devices, the unrecognisably changed landscape of front-end tooling.\n\nTools and technologies come and go, but one thing has remained constant for me over the past decade: progressive enhancement.\n\nProgressive enhancement isn\u2019t a technology. It\u2019s more like a way of thinking. Instead of thinking about the specifics of how a finished website might look, progressive enhancement encourages you to think about the fundamental meaning of what the website is providing. So instead of thinking of a website in terms of its ideal state in a modern browser on a nice widescreen device, progressive enhancement allows you to think about the core functionality in a more abstract way.\n\nOnce you\u2019ve figured out what the core functionality is \u2013 adding an item to a shopping cart, posting a message, sharing a photo \u2013 then you can enable that functionality in the simplest possible way. That usually means starting with good old-fashioned HTML. Links and forms are often all you need. Then, once you have the core functionality working in a basic way, you can start to enhance to make a progressively better experience for more modern browsers.\n\nThe advantage of working this way isn\u2019t just that your site will work in older browsers (albeit in a rudimentary way). It also ensures that if anything goes wrong in a modern browser, it won\u2019t be catastrophic.\n\nThere\u2019s a common misconception that progressive enhancement means that you\u2019ll spend your time dealing with older browsers, but in fact the opposite is true. Putting the basic functionality into place doesn\u2019t take very long at all. And once you\u2019ve done that, you\u2019re free to spend all your time experimenting with the latest and greatest browser technologies, secure in the knowledge that even if they aren\u2019t universally supported yet, that\u2019s OK: you\u2019ve already got your fallback in place.\n\nThe key to thinking about web development this way is realising that there isn\u2019t one final interface \u2013 there could be many, slightly different interfaces depending on the properties and capabilities of any particular user agent at any particular moment. And that\u2019s OK. Websites do not need to look the same in every browser.\n\nOnce you truly accept that, it\u2019s an immensely liberating idea. Instead of spending your time trying to make websites look the same in wildly varying browsers, you can spend your time making sure that the core functionality of what you build works everywhere, while providing the best possible experience for more capable browsers.\n\nAllow me to demonstrate with a simple example: navigation.\n\nStep one: core functionality\n\nLet\u2019s say we have a straightforward website about the twelve days of Christmas, with a page for each day. The core functionality is pretty clear:\n\n\n\tTo read about any particular day.\n\tTo browse from day to day.\n\n\nThe first is easily satisfied by marking up the text with headings, paragraphs and all the usual structural HTML elements. The second is satisfied by providing a list of good ol\u2019 hyperlinks.\n\nNow where\u2019s the best place to position this navigation list? Personally, I\u2019m a big fan of the jump-to-footer pattern. This puts the content first and the navigation second. At the top of the page there\u2019s a link with an href attribute pointing to the fragment identifier for the navigation.\n\n\n

\n Menu\n ...\n

\n \n\n\nSee the footer-anchor pattern in action.\n\nBecause it\u2019s nothing more than a hyperlink, this works in just about every browser since the dawn of the web. Following hyperlinks is what web browsers were made to do (hence the name).\n\nStep two: layout as an enhancement\n\nThe footer-anchor pattern is a particularly neat solution on small-screen devices, like mobile phones. Once more screen real estate is available, I can use the magic of CSS to reposition the navigation above the content. I could use position: absolute, flexbox or, in this case, display: table.\n\n@media all and (min-width: 35em) {\n .control {\n display: none;\n }\n body {\n display: table;\n }\n [role=\"navigation\"] {\n display: table-caption;\n columns: 6 15em;\n }\n}\n\nSee the styles for wider screens in action\n\nStep three: enhance!\n\nRight. At this point I\u2019m providing core functionality to everyone, and I\u2019ve got nice responsive styles for wider screens. I could stop here, but the real advantage of progressive enhancement is that I don\u2019t have to. From here on, I can go crazy adding all sorts of fancy enhancements for modern browsers, without having to worry about providing a fallback for older browsers \u2013 the fallback is already in place.\n\nWhat I\u2019d really like is to provide a swish off-canvas pattern for small-screen devices. Here\u2019s my plan:\n\n\n\tPosition the navigation under the main content.\n\tListen out for the .control links being activated and intercept that action.\n\tWhen those links are activated, toggle a class of .active on the body.\n\tIf the .active class exists, slide the content out to reveal the navigation.\n\n\nHere\u2019s the CSS for positioning the content and navigation:\n\n@media all and (max-width: 35em) {\n [role=\"main\"] {\n transition: all .25s;\n width: 100%;\n position: absolute;\n z-index: 2;\n top: 0;\n right: 0;\n }\n [role=\"navigation\"] {\n width: 75%;\n position: absolute;\n z-index: 1;\n top: 0;\n right: 0;\n }\n .active [role=\"main\"] {\n transform: translateX(-75%);\n }\n}\n\nIn my JavaScript, I\u2019m going to listen out for any clicks on the .control links and toggle the .active class on the body accordingly:\n\n(function (win, doc) {\n 'use strict';\n var linkclass = 'control',\n activeclass = 'active',\n toggleClassName = function (element, toggleClass) {\n var reg = new RegExp('(s|^)' + toggleClass + '(s|$)');\n if (!element.className.match(reg)) {\n element.className += ' ' + toggleClass;\n } else {\n element.className = element.className.replace(reg, '');\n }\n },\n navListener = function (ev) {\n ev = ev || win.event;\n var target = ev.target || ev.srcElement;\n if (target.className.indexOf(linkclass) !== -1) {\n ev.preventDefault();\n toggleClassName(doc.body, activeclass);\n }\n };\n doc.addEventListener('click', navListener, false);\n}(this, this.document));\n\nI\u2019m all set, right? Not so fast!\n\nCutting the mustard\n\nI\u2019ve made the assumption that addEventListener will be available in my JavaScript. That isn\u2019t a safe assumption. That\u2019s because JavaScript \u2013 unlike HTML or CSS \u2013 isn\u2019t fault-tolerant. If you use an HTML element or attribute that a browser doesn\u2019t understand, or if you use a CSS selector, property or value that a browser doesn\u2019t understand, it\u2019s no big deal. The browser will just ignore what it doesn\u2019t understand: it won\u2019t throw an error, and it won\u2019t stop parsing the file.\n\nJavaScript is different. If you make an error in your JavaScript, or use a JavaScript method or property that a browser doesn\u2019t recognise, that browser will throw an error, and it will stop parsing the file. That\u2019s why it\u2019s important to test for features before using them in JavaScript. That\u2019s also why it isn\u2019t safe to rely on JavaScript for core functionality.\n\nIn my case, I need to test for the existence of addEventListener:\n\n(function (win, doc) {\n if (!win.addEventListener) {\n return;\n }\n ...\n}(this, this.document));\n\nThe good folk over at the BBC call this kind of feature test cutting the mustard. If a browser passes the test, it cuts the mustard, and so it gets the enhancements. If a browser doesn\u2019t cut the mustard, it doesn\u2019t get the enhancements. And that\u2019s fine because, remember, websites don\u2019t need to look the same in every browser.\n\nI want to make sure that my off-canvas styles are only going to apply to mustard-cutting browsers. I\u2019m going to use JavaScript to add a class of .cutsthemustard to the document:\n\n(function (win, doc) {\n if (!win.addEventListener) {\n return;\n }\n ...\n var enhanceclass = 'cutsthemustard';\n doc.documentElement.className += ' ' + enhanceclass;\n}(this, this.document));\n\nNow I can use the existence of that class name to adjust my CSS:\n\n@media all and (max-width: 35em) {\n .cutsthemustard [role=\"main\"] {\n transition: all .25s;\n width: 100%;\n position: absolute;\n z-index: 2;\n top: 0;\n right: 0;\n }\n .cutsthemustard [role=\"navigation\"] {\n width: 75%;\n position: absolute;\n z-index: 1;\n top: 0;\n right: 0;\n }\n .cutsthemustard .active [role=\"main\"] {\n transform: translateX(-75%);\n }\n}\n\nSee the enhanced mustard-cutting off-canvas navigation. Remember, this only applies to small screens so you might have to squish your browser window.\n\nEnhance all the things!\n\nThis was a relatively simple example, but it illustrates the thinking behind progressive enhancement: once you\u2019re providing the core functionality to everyone, you\u2019re free to go crazy with all the latest enhancements for modern browsers.\n\nProgressive enhancement doesn\u2019t mean you have to provide all the same functionality to everyone \u2013 quite the opposite. That\u2019s why it\u2019s key to figure out early on what the core functionality is, and make sure that it can be provided with the most basic technology. But from that point on, you\u2019re free to add many more features that aren\u2019t mission-critical. You should reward more capable browsers by giving them more of those features, such as animation in CSS, geolocation in JavaScript, and new input types in HTML.\n\nLike I said, progressive enhancement isn\u2019t a technology. It\u2019s a way of thinking. Once you start thinking this way, you\u2019ll be prepared for whatever the next ten years throws at us.", "year": "2014", "author": "Jeremy Keith", "author_slug": "jeremykeith", "published": "2014-12-09T00:00:00+00:00", "url": "https://24ways.org/2014/responsive-enhancement/", "topic": "code"}