rowid,title,contents,year,author,author_slug,published,url,topic 157,Capturing Caps Lock,"One of the more annoying aspects of having to remember passwords (along with having to remember loads of them) is that if you’ve got Caps Lock turned on accidentally when you type one in, it won’t work, and you won’t know why. Most desktop computers alert you in some way if you’re trying to enter your password to log on and you’ve enabled Caps Lock; there’s no reason why the web can’t do the same. What we want is a warning – maybe the user wants Caps Lock on, because maybe their password is in capitals – rather than something that interrupts what they’re doing. Something subtle. But that doesn’t answer the question of how to do it. Sadly, there’s no way of actually detecting whether Caps Lock is on directly. However, there’s a simple work-around; if the user presses a key, and it’s a capital letter, and they don’t have the Shift key depressed, why then they must have Caps Lock on! Simple. DOM scripting allows your code to be notified when a key is pressed in an element; when the key is pressed, you get the ASCII code for that key. Capital letters, A to Z, have ASCII codes 65 to 90. So, the code would look something like: on a key press if the ASCII code for the key is between 65 and 90 *and* if shift is pressed warn the user that they have Caps Lock on, but let them carry on end if end keypress The actual JavaScript for this is more complicated, because both event handling and keypress information differ across browsers. Your event handling functions are passed an event object, except in Internet Explorer where you use the global event object; the event object has a which parameter containing the ASCII code for the key pressed, except in Internet Explorer where the event object has a keyCode parameter; some browsers store whether the shift key is pressed in a shiftKey parameter and some in a modifiers parameter. All this boils down to code that looks something like this: keypress: function(e) { var ev = e ? e : window.event; if (!ev) { return; } var targ = ev.target ? ev.target : ev.srcElement; // get key pressed var which = -1; if (ev.which) { which = ev.which; } else if (ev.keyCode) { which = ev.keyCode; } // get shift status var shift_status = false; if (ev.shiftKey) { shift_status = ev.shiftKey; } else if (ev.modifiers) { shift_status = !!(ev.modifiers & 4); } // At this point, you have the ASCII code in “which”, // and shift_status is true if the shift key is pressed } Then it’s just a check to see if the ASCII code is between 65 and 90 and the shift key is pressed. (You also need to do the same work if the ASCII code is between 97 (a) and 122 (z) and the shift key is not pressed, because shifted letters are lower-case if Caps Lock is on.) if (((which >= 65 && which <= 90) && !shift_status) || ((which >= 97 && which <= 122) && shift_status)) { // uppercase, no shift key /* SHOW THE WARNING HERE */ } else { /* HIDE THE WARNING HERE */ } The warning can be implemented in many different ways: highlight the password field that the user is typing into, show a tooltip, display text next to the field. For simplicity, this code shows the warning as a previously created image, with appropriate alt text. Showing the warning means creating a new tag with DOM scripting, dropping it into the page, and positioning it so that it’s next to the appropriate field. The image looks like this: You know the position of the field the user is typing into (from its offsetTop and offsetLeft properties) and how wide it is (from its offsetWidth properties), so use createElement to make the new img element, and then absolutely position it with style properties so that it appears in the appropriate place (near to the text field). The image is a transparent PNG with an alpha channel, so that the drop shadow appears nicely over whatever else is on the page. Because Internet Explorer version 6 and below doesn’t handle transparent PNGs correctly, you need to use the AlphaImageLoader technique to make the image appear correctly. newimage = document.createElement('img'); newimage.src = ""http://farm3.static.flickr.com/2145/2067574980_3ddd405905_o_d.png""; newimage.style.position = ""absolute""; newimage.style.top = (targ.offsetTop - 73) + ""px""; newimage.style.left = (targ.offsetLeft + targ.offsetWidth - 5) + ""px""; newimage.style.zIndex = ""999""; newimage.setAttribute(""alt"", ""Warning: Caps Lock is on""); if (newimage.runtimeStyle) { // PNG transparency for IE newimage.runtimeStyle.filter += ""progid:DXImageTransform.Microsoft.AlphaImageLoader(src='http://farm3.static.flickr.com/2145/2067574980_3ddd405905_o_d.png',sizingMethod='scale')""; } document.body.appendChild(newimage); Note that the alt text on the image is also correctly set. Next, all these parts need to be pulled together. On page load, identify all the password fields on the page, and attach a keypress handler to each. (This only needs to be done for password fields because the user can see if Caps Lock is on in ordinary text fields.) var inps = document.getElementsByTagName(""input""); for (var i=0, l=inps.length; i The “create an image” code from above should only be run if the image is not already showing, so instead of creating a newimage object, create the image and attach it to the password field so that it can be checked for later (and not shown if it’s already showing). For safety, all the code should be wrapped up in its own object, so that its functions don’t collide with anyone else’s functions. So, create a single object called capslock and make all the functions be named methods of the object: var capslock = { ... keypress: function(e) { } ... } Also, the “create an image” code is saved into its own named function, show_warning(), and the converse “remove the image” code into hide_warning(). This has the advantage that developers can include the JavaScript library that has been written here, but override what actually happens with their own code, using something like: And that’s all. Simply include the JavaScript library in your pages, override what happens on a warning if that’s more appropriate for what you’re doing, and that’s all you need. See the script in action.",2007,Stuart Langridge,stuartlangridge,2007-12-04T00:00:00+00:00,https://24ways.org/2007/capturing-caps-lock/,code 168,Unobtrusively Mapping Microformats with jQuery,"Microformats are everywhere. You can’t shake an electronic stick these days without accidentally poking a microformat-enabled site, and many developers use microformats as a matter of course. And why not? After all, why invent your own class names when you can re-use pre-defined ones that give your site extra functionality for free? Nevertheless, while it’s good to know that users of tools such as Tails and Operator will derive added value from your shiny semantics, it’s nice to be able to reuse that effort in your own code. We’re going to build a map of some of my favourite restaurants in Brighton. Fitting with the principles of unobtrusive JavaScript, we’ll start with a semantically marked up list of restaurants, then use JavaScript to add the map, look up the restaurant locations and plot them as markers. We’ll be using a couple of powerful tools. The first is jQuery, a JavaScript library that is ideally suited for unobtrusive scripting. jQuery allows us to manipulate elements on the page based on their CSS selector, which makes it easy to extract information from microformats. The second is Mapstraction, introduced here by Andrew Turner a few days ago. We’ll be using Google Maps in the background, but Mapstraction makes it easy to change to a different provider if we want to later. Getting Started We’ll start off with a simple collection of microformatted restaurant details, representing my seven favourite restaurants in Brighton. The full, unstyled list can be seen in restaurants-plain.html. Each restaurant listing looks like this:
  • Riddle & Finns

    12b Meeting House Lane

    Brighton, UK

    BN1 1HB

    Telephone: +44 (0)1273 323 008

    E-mail: info@riddleandfinns.co.uk

  • Since we’re dealing with a list of restaurants, each hCard is marked up inside a list item. Each restaurant is an organisation; we signify this by placing the classes fn and org on the element surrounding the restaurant’s name (according to the hCard spec, setting both fn and org to the same value signifies that the hCard represents an organisation rather than a person). The address information itself is contained within a div of class adr. Note that the HTML
    element is not suitable here for two reasons: firstly, it is intended to mark up contact details for the current document rather than generic addresses; secondly, address is an inline element and as such cannot contain the paragraphs elements used here for the address information. A nice thing about microformats is that they provide us with automatic hooks for our styling. For the moment we’ll just tidy up the whitespace a bit; for more advanced style tips consult John Allsop’s guide from 24 ways 2006. .vcard p { margin: 0; } .adr { margin-bottom: 0.5em; } To plot the restaurants on a map we’ll need latitude and longitude for each one. We can find this out from their address using geocoding. Most mapping APIs include support for geocoding, which means we can pass the API an address and get back a latitude/longitude point. Mapstraction provides an abstraction layer around these APIs which can be included using the following script tag: While we’re at it, let’s pull in the other external scripts we’ll be using: That’s everything set up: let’s write some JavaScript! In jQuery, almost every operation starts with a call to the jQuery function. The function simulates method overloading to behave in different ways depending on the arguments passed to it. When writing unobtrusive JavaScript it’s important to set up code to execute when the page has loaded to the point that the DOM is available to be manipulated. To do this with jQuery, pass a callback function to the jQuery function itself: jQuery(function() { // This code will be executed when the DOM is ready }); Initialising the map The first thing we need to do is initialise our map. Mapstraction needs a div with an explicit width, height and ID to show it where to put the map. Our document doesn’t currently include this markup, but we can insert it with a single line of jQuery code: jQuery(function() { // First create a div to host the map var themap = jQuery('
    ').css({ 'width': '90%', 'height': '400px' }).insertBefore('ul.restaurants'); }); While this is technically just a single line of JavaScript (with line-breaks added for readability) it’s actually doing quite a lot of work. Let’s break it down in to steps: var themap = jQuery('
    ') Here’s jQuery’s method overloading in action: if you pass it a string that starts with a < it assumes that you wish to create a new HTML element. This provides us with a handy shortcut for the more verbose DOM equivalent: var themap = document.createElement('div'); themap.id = 'themap'; Next we want to apply some CSS rules to the element. jQuery supports chaining, which means we can continue to call methods on the object returned by jQuery or any of its methods: var themap = jQuery('
    ').css({ 'width': '90%', 'height': '400px' }) Finally, we need to insert our new HTML element in to the page. jQuery provides a number of methods for element insertion, but in this case we want to position it directly before the