{"rowid": 168, "title": "Unobtrusively Mapping Microformats with jQuery", "contents": "Microformats are everywhere. You can\u2019t 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?\n\nNevertheless, while it\u2019s good to know that users of tools such as Tails and Operator will derive added value from your shiny semantics, it\u2019s nice to be able to reuse that effort in your own code.\n\nWe\u2019re going to build a map of some of my favourite restaurants in Brighton. Fitting with the principles of unobtrusive JavaScript, we\u2019ll 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.\n\nWe\u2019ll 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.\n\nThe second is Mapstraction, introduced here by Andrew Turner a few days ago. We\u2019ll be using Google Maps in the background, but Mapstraction makes it easy to change to a different provider if we want to later.\n\nGetting Started\n\nWe\u2019ll 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:\n\n
  • \n\t

    Riddle & Finns

    \n\t
    \n\t\t

    12b Meeting House Lane

    \n\t\t

    Brighton, UK

    \n\t\t

    BN1 1HB

    \n\t
    \n\t

    Telephone: +44 (0)1273 323 008

    \n\t

    E-mail: info@riddleandfinns.co.uk

    \n
  • \n\nSince we\u2019re 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\u2019s 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).\n\nThe 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.\n\nA nice thing about microformats is that they provide us with automatic hooks for our styling. For the moment we\u2019ll just tidy up the whitespace a bit; for more advanced style tips consult John Allsop\u2019s guide from 24 ways 2006.\n\n.vcard p {\n\tmargin: 0;\n}\n.adr {\n\tmargin-bottom: 0.5em;\n}\n\nTo plot the restaurants on a map we\u2019ll 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:\n\n\n\nWhile we\u2019re at it, let\u2019s pull in the other external scripts we\u2019ll be using:\n\n\n\n\n\n\nThat\u2019s everything set up: let\u2019s write some JavaScript!\n\nIn 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\u2019s 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:\n\njQuery(function() {\n\t// This code will be executed when the DOM is ready\n});\n\nInitialising the map\n\nThe 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\u2019t currently include this markup, but we can insert it with a single line of jQuery code:\n\njQuery(function() {\n\t// First create a div to host the map\n\tvar themap = jQuery('
    ').css({\n\t\t'width': '90%',\n\t\t'height': '400px'\n\t}).insertBefore('ul.restaurants');\n});\n\nWhile this is technically just a single line of JavaScript (with line-breaks added for readability) it\u2019s actually doing quite a lot of work. Let\u2019s break it down in to steps:\n\nvar themap = jQuery('
    ')\n\nHere\u2019s jQuery\u2019s 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:\n\nvar themap = document.createElement('div');\nthemap.id = 'themap';\n\nNext 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:\n\nvar themap = jQuery('
    ').css({\n\t'width': '90%',\n\t'height': '400px'\n})\n\nFinally, 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