How do I filter results with multiple select groups using jQuery?

Question

I have two options that I am trying to filter between now, but will be adding in a third and maybe a fourth later on (for example: right now I am filtering between prices and reviews but will want to add more prices to the list and also another filter category like "rating" which would consist of 3, 4, or 5 stars).

Using the logic that I have listed below works fine, but I feel it will get really long and complicated (and unnecessary) as I go. I know there is a way to refactor the code I'm just wondering what the best way to go about it would be? HTML:

  <select class="deals">
    <option value="deals-all">All deals</option>
    <option value="50">$50</option>
    <option value="25">$25</option>
  </select>

  <select class="reviews">
    <option value="reviews-all">All reviews</option>
    <option value="reviews-positive">Positive reviews</option>
    <option value="reviews-negative">Negative reviews</option>
  </select>

jQuery

 $('.reviews, .deals').change(function() {

var reviewsVal = $('.reviews :selected').val();
var dealsVal = $('.deals :selected').val();



 if((reviewsVal == 'reviews-all') && (dealsVal == 'deals-all')) {

      $('.review-positive').show();
 $('.review-negative').show();
 $('.deals-25').show();
 $('.deals-50').show();
 } 


else if((dealsVal == '50') && (reviewsVal == 'reviews-positive')) {
 $('.review-negative.deals-50').hide();
 $('.review-positive.deals-50').show();
 $('.review-negative.deals-25').hide();
 $('.review-positive.deals-25').hide();

 }

 else if((dealsVal == '50') && (reviewsVal == 'reviews-negative')) {
 $('.review-negative.deals-50').show();
 $('.review-positive.deals-50').hide();
 $('.review-negative.deals-25').hide();
 $('.review-positive.deals-25').hide();
 }

else if((dealsVal == '25') && (reviewsVal == 'reviews-positive')) {
 $('.review-negative.deals-50').hide();
 $('.review-positive.deals-50').hide();
 $('.review-negative.deals-25').hide();
 $('.review-positive.deals-25').show();
}

else if((dealsVal == '25') && (reviewsVal == 'reviews-negative')) {
 $('.review-negative.deals-50').hide();
 $('.review-positive.deals-50').hide();
 $('.review-negative.deals-25').show();
 $('.review-positive.deals-25').hide();
}

 else if((dealsVal == 'deals-all') && (reviewsVal == 'reviews-positive')) {
 $('.review-negative.deals-50').hide();
 $('.review-positive.deals-50').show();
 $('.review-negative.deals-25').hide();
 $('.review-positive.deals-25').show();
}

else if((dealsVal == 'deals-all') && (reviewsVal == 'reviews-negative')) {
 $('.review-negative.deals-50').show();
 $('.review-positive.deals-50').hide();
 $('.review-negative.deals-25').show();
 $('.review-positive.deals-25').hide();
}

else if((dealsVal == '50') && (reviewsVal == 'reviews-all')) {
 $('.review-negative.deals-50').show();
 $('.review-positive.deals-50').show();
 $('.review-negative.deals-25').hide();
 $('.review-positive.deals-25').hide();
}

else if((dealsVal == '25') && (reviewsVal == 'reviews-all')) {
 $('.review-negative.deals-50').hide();
 $('.review-positive.deals-50').hide();
 $('.review-negative.deals-25').show();
 $('.review-positive.deals-25').show();
}

else {
 $('.review-positive').show();
 $('.review-negative').show();
 $('.deals-25').show();
 $('.deals-50').show();
} 
});

$('.reviews-positive').click(function() {
$('.review-negative').hide();
$('.review-positive').show();
});

$('.reviews-negative').click(function() {
$('.review-positive').hide();
$('.review-negative').show();
});


});​

Hopefully you can see what I am going for, thanks for any input.

*EDIT: jsfiddle: http://jsfiddle.net/TXywp/1/

Answer 1

I can think of two different approaches to simplify the code and make it easier to maintain and grow:

1. You can algorithmically derive what items should be hidden or shown based on the conditions.

2. You can create a table of conditions and actions so that adding a new condition and action is just adding a new item to the table.

3. Change your HTML to make it self-describing for what it should display.

Here's what the table driven approach looks like:

$('.reviews, .deals').change(function() {

    var allDeals = '.review-negative.deals-50, .review-positive.deals-50, .review-positive.deals-25, .review-negative.deals-25';

    var table = [
        {rv: 'reviews-all', dv: 'deals-all', show: '.review-positive, .review-negative, .deals-25, .deals-50'},
        {rv: 'reviews-positive', dv: '50', show: '.review-positive.deals-50'},
        {rv: 'reviews-negative', dv: '50', show: '.review-negative.deals-50'},
        {rv: 'reviews-positive', dv: '25', show: '.review-positive.deals-25'}
        {rv: 'reviews-negative', dv: '25', show: '.review-negative.deals-25'},
        {rv: 'reviews-positive', dv: 'deals-all', show: '.review-positive.deals-50, .review-positive.deals-25'},
        {rv: 'reviews-negative', dv: 'deals-all', show: '.review-negative.deals-50, .review-negative.deals-25'},
        {rv: 'reviews-all', dv: '50', show: '.review-negative.deals-50, .review-positive.deals-50'},
        {rv: 'reviews-all', dv: '25', show: '.review-negative.deals-25, .review-positive.deals-25'}
    ];

    var reviewsVal = $('.reviews :selected').val();
    var dealsVal = $('.deals :selected').val();

    $(allDeals).hide();

    var item, found = false;
    for (var i = 0, len = table.length; i < len; i++) {
        item = table[i];
        if (dealsVal == item.dv && reviewsVal == item.rv) {
            $(item.show).show();
            found = true;
            break;
        }
    }

    if (!found) {
        $('.review-positive, .review-negative, .deals-25, .deals-50').show();
    } 
});

And, here's an algorithmic way that lets you add a new deal value by just adding one new entry to an array. With only two deals, this is probably more work than the table driven approach, but if you had 4 or more deal levels, this would a lot simpler to maintain.

$('.reviews, .deals').change(function() {
    var deals = ['25', '50'];

    function addAllDeals(base, prefix) {
        for (var i = 0; i < deals.length; i++) {
            if (base) base += ", ";
            base += prefix + deals[i];
        }
        return(base);
    }

    function addSingleDeal(prefixes, deal) {
        var sel = [];
        for (var i = 0; i < prefixes.length; i++) {
            sel.push(prefixes[i] + deal);
        }
        return(sel.join(", ");
    }

    var reviewsVal = $('.reviews :selected').val();
    var dealsVal = $('.deals :selected').val();
    var itemsToShow = "";

    // hide everything to start
    var initialHide = addAllDeals("", ".review-positive.deals-");
    initialHide = addAllDeals(initialHide, ".review-negative.deals-");
    $(initialHide).hide();

    if (reviewsVal == 'reviews-all') {
        if (dealsVal == 'deals-all') {
            itemsToShow = addAllDeals(".review-positive, .review-negative", ".deals-");
        } else {
            itemsToShow = addSingleDeal([".review-negative.deals-", ".review-negative.deals-"], dealsVal);
        }
    } else if (reviewsVal == 'reviews-positive') {
        itemsToShow = '.review-positive.deals-' + dealsVal;
    } else if (reviewVal == 'reviews-negative') {
        itemsToShow = '.review-negative.deals-' + dealsVal;
    } else {
        itemsToShow = addAllDeals(".review-positive, .review-negative", ".deals-");
    }
});

If you can change your HTML (as in my third option above) to this:

  <select class="deals">
    <option value="deals-all" data-base=".review-positive, .review-negative">All deals</option>
    <option value="50" data-base=".deals-50">$50</option>
    <option value="25" data-base=".deals-25">$25</option>
  </select>

  <select class="reviews">
    <option value="reviews-all" data-filter="">All reviews</option>
    <option value="reviews-positive" data-filter=".review-positive">Positive reviews</option>
    <option value="reviews-negative" data-filter=".review-negative">Negative reviews</option>
  </select>

Then, you can just use this simple javascript:

 $('.reviews, .deals').change(function() {

    var dealsBase = $('.deals :selected').data("base");
    var reviewsFilter = $('.reviews :selected').data("filter");

     // hide all
     $(".review-negative, .review-positive").hide();

     // show the desired ones
     var base = $(dealsBase);
     if (reviewsFilter) {
         base = base.filter(reviewsFilter);
     }
     base.show();
});

Caveat: Since you did not provide a working jsFiddle example of your code/HTML to try this with, this code has not been run or checked for typing errors. But, hopefully you get the idea of the two approaches.

Answer 2

To get a dynamic result a standardized naming is the best way to go. You start by standardizing the criteria selectors, giving them a general class and differentiating with id properties. Following a naming convetion for values is also recommended. This would produce something in the lines of

    <select id="deal" class="criteriaSelector">
      <option value="all">All deals</option>
      <option value="50">$50</option>
      <option value="25">$25</option>
    </select>

    <select id="review" class="criteriaSelector">
      <option value="all">All reviews</option>
      <option value="positive">Positive reviews</option>
      <option value="negative">Negative reviews</option>
    </select>

Then you give all the items you want to filter a generic class besides the filtering classes. I will use .item as an example. You will also want to be able to construct the class from selected value and criteria name so using the .{id}-{value} system will work perfectly. This will leave us with something in the lines of

    <div class="item review-positive deal-25"></div>
    <div class="item review-negative deal-50"></div>

This setup will allow us to build dynamic and extensible code:

    $('.criteriaSelector').change(function() {
      // Initialize criteria string
      var criteria = '';
      // Set value for all selector
      var showAll = true;

      // Iterate over all criteriaSelectors
      $('.criteriaSelector').each(function(){
        // Get value
        var val = $(this).children(':selected').val();
        // Check if this limits our results
        if(val !== 'all'){
          // Append selector to criteria
          criteria += '.' + $(this).attr('id') + '-' + val;
          // We don't want to show all results anymore
          showAll = false;
        }
      });
      // Check if results are limited somehow
      if(showAll){
        // No criterias were set so show all
        $('.item').show();
      } else {
        // Hide all items
        $('.item').hide();
        // Show the ones that were selected
        $(criteria).show();
      }

    });

Now adding a new criteria selector won't require changes in this piece of code as long as naming conventions are followed.