Fixing filters logic + adding titles to button for accessibility

static/css/main.css

@@ -122,7 +122,7 @@ a {
   background-color: transparent;
   border: 2px solid white;
   overflow: visible;
-  color: #444;
+  color: white;
   font: inherit;
   padding: .5rem 1.5rem;
   margin: .5rem 1rem;
@@ -131,9 +131,9 @@ a {
   .mg-tag-filter:hover {
     border-color: #b2b2b2;
     text-decoration: none; }
-  .mg-tag-filter-enabled {
+  .mg-tag-filter-include {
     background-color: #33b5e5; }
-  .mg-tag-filter-disabled {
+  .mg-tag-filter-exclude {
     background-color: #FF9148;  }
 
 .mg-nav-small {

templates/index.html

@@ -6,11 +6,11 @@
 {% if MG_LANG_FILTER_TAGS or MG_FILTER_TAGS %}
 <ul class="mg-tag-filters">
 {% if MG_LANG_FILTER_TAGS %}
-<li><button class="mg-tag-filter" onclick='toggleLangTagFilter.bind(this)({{ MG_LANG_FILTER_TAGS|tojson }})'>lang</button></li>
+<li><button class="mg-tag-filter" onclick='toggleLangTagFilter.bind(this)({{ MG_LANG_FILTER_TAGS|tojson }})' title="Language filter (disabled)">lang</button></li>
 {% endif %}
 {% if MG_FILTER_TAGS %}
 {% for filter_tag in MG_FILTER_TAGS %}
-<li><button class="mg-tag-filter" onclick="toggleTagFilter.bind(this)('{{ filter_tag }}')">{{ filter_tag.replace('lang:', '') }}</button></li>
+<li><button class="mg-tag-filter" onclick="toggleTagFilter.bind(this)('{{ filter_tag }}')" title="Tag filter (disabled)">{{ filter_tag.replace('lang:', '') }}</button></li>
 {% endfor %}
 </ul>
 {% endif %}

templates/js/filter-tags.js

@@ -9,23 +9,25 @@ window.tagFilters = {}
 function indexOf(array, predicate) {
     for (var i = 0; i < array.length; i++) if (predicate(array[i])) return array[i];
 }
-function startsWith(searchString, position) {
+function includes(array, value) {
-    position = position || 0;
+    return array.indexOf(value) !== -1;
-    return this.substr(position, searchString.length) === searchString;
 };
 
 function toggleTagFilter(tag) {
     var filterState = window.tagFilters[tag]
     if (filterState === true) {
-        this.classList.remove('mg-tag-filter-enabled');
+        this.classList.remove('mg-tag-filter-exclude');
         filterState = false;
-        this.classList.add('mg-tag-filter-disabled');
+        this.classList.add('mg-tag-filter-include');
+        this.title = 'Tag filter (include matching articles)';
     } else if (filterState === false) {
-        this.classList.remove('mg-tag-filter-disabled');
+        this.classList.remove('mg-tag-filter-include');
         filterState = undefined;
+        this.title = 'Tag filter (disabled)';
     } else {
         filterState = true;
-        this.classList.add('mg-tag-filter-enabled');
+        this.classList.add('mg-tag-filter-exclude');
+        this.title = 'Tag filter (exclude matching articles)';
     }
     window.tagFilters[tag] = filterState;
     updateArticlesVisibility();
@@ -33,38 +35,38 @@ function toggleTagFilter(tag) {
 
 function toggleLangTagFilter(langs) {
     var lang = this.textContent;
-    if (lang === 'lang') {
-        lang = langs[0];
-        window.tagFilters['lang:'+lang] = true;
-    } else {
     window.tagFilters['lang:'+lang] = undefined;
     lang = langs[langs.indexOf(lang) + 1];
     if (typeof lang === 'undefined') {
         lang = 'lang'
+        this.title = 'Language filter (disabled)';
     } else {
         window.tagFilters['lang:'+lang] = true;
-        }
+        this.title = 'Language filter (include only "' + lang + '" articles)';
     }
     this.textContent = lang;
     updateArticlesVisibility();
 }
 
 function updateArticlesVisibility() {
-    var anyTrueFilter = Object.keys(window.tagFilters).some(function (tagFilter) {
+    var includeFilters = Object.keys(window.tagFilters).filter(function (tagFilter) {
-        return !!window.tagFilters[tagFilter];
+        return window.tagFilters[tagFilter] === true;
+    });
+    var excludeFilters = Object.keys(window.tagFilters).filter(function (tagFilter) {
+        return window.tagFilters[tagFilter] === false;
     });
     Array.prototype.slice.call(document.getElementsByTagName('article')).forEach(function (article) {
         if (!article.dataset.tags) { // article-excerpt: we ignore it
             return;
         }
         var articleTags = JSON.parse(article.dataset.tags);
-        var anyTagWhitelisted = articleTags.some(function (tag) { return window.tagFilters[tag] === true; });
+        var allIncludeTags = includeFilters.every(function (tag) { return includes(articleTags, tag); });
-        var anyTagBlacklisted = articleTags.some(function (tag) { return window.tagFilters[tag] === false; });
+        var anyExcludeTag = excludeFilters.some(function (tag) { return includes(articleTags, tag); });
 
         // Now implementing the core logic
-        var shouldDisplay = !anyTagBlacklisted;
+        var shouldDisplay = !anyExcludeTag;
-        if (shouldDisplay && anyTrueFilter) {
+        if (shouldDisplay && includeFilters.length > 0) {
-            shouldDisplay = anyTagWhitelisted;
+            shouldDisplay = allIncludeTags;
         }
 
         if (shouldDisplay) {