JavaScript/jQuery could do with some improvement

Question

I am in the process of stripping down some code I've written for a Time Frame selector function that filters search results based on a selected Time Frame (Last Month, Last Quarter & Last Year) by hiding all irrelevant results based on when they were created. The function is called by a GET variable submitted on form submit ?time_frame_query=Last+Month

Now the code as is works, which is a start. However I feel it could be greatly improved, and unfortunately I have exhausted all options trying to do this myself. The problem I am having is that by the time I get to writing the functions for the Last Year filter, I am having to write a huge amount of code which I feel isn't entirely necessary. I have toyed with the idea of putting all the month variables into an array then putting together a specific "Last Month" "Last Quarter" "Last Year" function that will do the work for me. But again given my current knowledge of JS/jQuery, I simply do not know how to go about doing this.

Below is a snippet of code that I feel is relevant to my question and also helps illustrate the problem I am facing. Please let me know if you need to see any more.

EDIT: Thanks to Doug the entire working code can be found here: http://pastie.org/private/wl2qvnyar5xpibu4ot1lig

Any help/advice would be greatly appreciated.

var timezone = "Australia/ACT";
$.getJSON("http://json-time.appspot.com/time.json?tz="+timezone+"&callback=?",
  function(data){
    var datetime = data.datetime
      var date = datetime.split(" ")
      var day = date[1]
      var month = date[2]
      var year = date[3]
      var prevYear = year - 1
      var jan = 'Jan'
      //etc etc etc
      var dec = 'Dec'
      var timeFrame = $.getUrlVar('time_frame_query');
      switch(timeFrame){
      //****************************
      // Begin Last Quarter function
      //****************************
      case 'Last+Quarter': 
        switch(month){
          case 'Jan':
            $('#searchResults div.'+oct+prevYear+',#searchResults div.'+nov+prevYear+',#searchResults div.'+dec+prevYear+',#searchResults div.'+jan+year).show();
            break;
          case 'Feb':
            $('#searchResults div.'+nov+prevYear+',#searchResults div.'+dec+prevYear+',#searchResults div.'+jan+year+',#searchResults div.'+feb+year).show();
            break;
          case 'Mar':
            $('#searchResults div.'+dec+prevYear+',#searchResults div.'+jan+year+',#searchResults div.'+feb+year+',#searchResults div.'+mar+year).show();
            break;
          case 'Apr':
            $('#searchResults div.'+jan+year+',#searchResults div.'+feb+year+',#searchResults div.'+mar+year+',#searchResults div.'+apr+year).show();
            break;
            // etc etc etc
        }
        break;

Appologies for the poorly formatted code above, first submission to this site. WYSIWYG FTL! :(

Answer 1

Try datejs, library that parses date strings and return actual dates. It is really flexible and understand last/next concept. It doesn't know what quarter is though so you might have to tweak it, there's an API if I'm not mistaken.

Answer 2

OK, here is my best shot for how tired I am :) A couple things in general. You need to end each line in a semicolon, that is really important. Also, my code assumes a four digit year (2009 vs 09). Without the rest of your site, its hard to test. Please let me know if you have any questions:

$(document).ready(function(){
  $.extend({
    getUrlVars: function(){
      var vars = [], hash;
      var hashes = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&');
      for(var i = 0; i < hashes.length; i++)
      {
        hash = hashes[i].split('=');
        vars.push(hash[0]);
        vars[hash[0]] = hash[1];
      }
      return vars;
    },
    getUrlVar: function(name){
      return $.getUrlVars()[name];
    }
  });
  var timezone = "Australia/ACT";
  $.getJSON("http://json-time.appspot.com/time.json?callback=?",
    { tz: timezone },
    function(data) {
      var datetime   = data.datetime,
          date       = datetime.split(" "),
          month      = date[2],
          year       = date[3],
          months     = ['Jan', 'Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec'],
          curr_month = $.inArray(month, months), // Zero based return
          curr       = new Date(year, curr_month),
          time_frame = $.getUrlVar('time_frame_query');

      $('#searchResults p.report-date').each(function(){
        var reportDate  = $(this).text(),
            dateExtract = reportDate.split(" "),
            month       = dateExtract[1],
            year        = dateExtract[2];

        $(this).parent().addClass(month + year).hide();
      });

      var buildSelector = function(date) {
          return "div." + months[date.getMonth()] + date.getFullYear();
      }

      var selectorRange = function(monthStart, monthRange, yearStart){
        var range = [];
        for(var i = monthRange; i <= 0; i++){
          range.push( buildSelector(new Date(yearStart, monthStart + i)));
        };
        return range;
      }

      var searchResults = $('#searchResults')[0];

      switch(time_frame){
        case 'Last+Month': 
          $( selectorRange( curr_month, -1, year).join(), searchResults ).show();
          break;

        case 'Last+Quarter': 
          $( selectorRange( curr_month, -3, year).join(), searchResults ).show();
          break;

        case 'Last+Year':
          $( selectorRange( curr_month, -12, year).join(), searchResults ).show();
          break;
      }
    });
});