generic keyboard navigation

jk-1.0.1.js

/*
 * Copyright © 2011 by Scott Perry
 * Released under the MIT License; its terms are at the end of this file.
 *
 * This file depends on:
 * • jQuery (tested against v1.4.2)
 *   http://jquery.com/
 *
 * To use this file, ensure that:
 * • jkInterestingElements() returns all available scroll targets
 * • jkKeys (or jkCodes) represent intended keybindings
 *
 * Inspiration provided by:
 * • jquery-jk
 *   by Pat Nakajima (patnakajima@gmail.com)
 *   https://github.com/nakajima/jquery-jk
 * • In Focus (The Atlantic) and The Big Picture (Boston Globe)
 *   by Alan Taylor (ataylor@theatlantic.com)
 *   http://www.theatlantic.com/infocus/
 *   http://www.boston.com/bigpicture/
 *
 * If you plan on using unusual keys (numpad, symbols, etc) and run into
 * cross-browser problems, chances are Jonathan Tang has solved this for you:
 *   https://github.com/nostrademons/keycode.js
 */

// elements that should be scroll targets
function jkInterestingElements() { return $("article"); }

// if you want to use non-character keys for navigation, override jkCodes below
var jkKeys = {
  NEXT: 'j',
  PREV: 'k'
};

/*****************************************************************************/

// specifically set keycodes override jkKeys
var jkCodes = {
  NEXT: jkKeys.NEXT.charCodeAt(),
  PREV: jkKeys.PREV.charCodeAt()
};

// worker function
function jkExecute(event) {
  // get the nearest (prev and next) elements of interest
  function closest() {
    // the elements of interest
    items = jkInterestingElements().filter(":visible");

    // defaults:
    // we can never scroll higher than the top of the page
    prev = $('html, body');
    // but we can potentially scroll lower than the last item
    next = null;
    
    items.each(function(index, item){
      // cache the distance, it gets used a lot
      itemdistance = $(item).offset().top - $(window).scrollTop();

      // update nearest previous item
      if(itemdistance < 0
      && ( prev == null
        || itemdistance > $(prev).offset().top - $(window).scrollTop()))
      {
        prev = item;
      }

      // update nearest next item
      if(itemdistance > 0
      && ( next == null
        || itemdistance < $(next).offset().top - $(window).scrollTop()))
      {
        next = item;
      }
    });
    
    return {next: next, prev: prev};
  }
  
  // nothing to do if there's no code
  if(!event.which) {
    return;
  }
  
  // avoid annoying the user
  if ($(event.target).is(':input')) {
    return;
  }

  /*
   * scroll to the appropriate location.
   *
   * could also use $('html, body').animate({scrollTop:pixels}, 'fast') but
   * it's not very responsive.
   */
  if(event.which == jkCodes.NEXT
  && closest().next != null)
  {
    $('html, body').scrollTop($(closest().next).offset().top);
  }
  if(event.which == jkCodes.PREV
  && closest().prev != null) {
    $('html, body').scrollTop($(closest().prev).offset().top);
  }
}

$(document).ready(function () {
  $(document).bind('keypress', jkExecute);
});

/*
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

jk-1.0.2.min.js

function jkInterestingElements(){return $("article")}
var jkKeys={NEXT:"j",PREV:"k"};
var jkCodes={NEXT:jkKeys.NEXT.charCodeAt(),PREV:jkKeys.PREV.charCodeAt()}

function jkExecute(a){function b(){items=jkInterestingElements().filter(":visible");prev=$("html, body");next=null;items.each(function(a,b){itemdistance=$(b).offset().top-$(window).scrollTop();if(itemdistance<0&&(prev==null||itemdistance>$(prev).offset().top-$(window).scrollTop())){prev=b}if(itemdistance>0&&(next==null||itemdistance<$(next).offset().top-$(window).scrollTop())){next=b}});return{next:next,prev:prev}}if(!a.which){return}if($(a.target).is(":input")){return}if(a.which==jkCodes.NEXT&&b().next!=null){$("html, body").scrollTop($(b().next).offset().top)}if(a.which==jkCodes.PREV&&b().prev!=null){$("html, body").scrollTop($(b().prev).offset().top)}}$(document).ready(function(){$(document).bind("keypress",jkExecute)})