Restructured initial 'if' statement for clarity

This was changed due to feedback by @benschwarz because the '!'(not) operator was easily missed and this method leaves less ambiguity to the intent of this file.

Author: knightdr

matchMedia.addListener.js

@@ -1,73 +1,75 @@
 /*! matchMedia() polyfill addListener/removeListener extension. Author & copyright (c) 2012: Scott Jehl. Dual MIT/BSD license */
 (function(){
-    // monkeypatch unsupported addListener/removeListener
-    if (window.matchMedia && !window.matchMedia('all').addListener){
-        var localMatchMedia = window.matchMedia,
-            hasMediaQueries = localMatchMedia('only all').matches,
-            isListening     = false,
-            timeoutID       = 0,    // setTimeout for debouncing 'handleChange'
-            queries         = [],   // Contains each 'mql' and associated 'listeners' if 'addListener' is used
-            handleChange    = function(evt) {
-                // Debounce
-                clearTimeout(timeoutID);
+    // Bail out for browsers that have addListener support
+    if (window.matchMedia && window.matchMedia('all').addListener) {
+        return false;
+    }
+
+    var localMatchMedia = window.matchMedia,
+        hasMediaQueries = localMatchMedia('only all').matches,
+        isListening     = false,
+        timeoutID       = 0,    // setTimeout for debouncing 'handleChange'
+        queries         = [],   // Contains each 'mql' and associated 'listeners' if 'addListener' is used
+        handleChange    = function(evt) {
+            // Debounce
+            clearTimeout(timeoutID);
 
-                timeoutID = setTimeout(function() {
-                    for (var i = 0, il = queries.length; i < il; i++) {
-                        var mql         = queries[i].mql,
-                            listeners   = queries[i].listeners || [],
-                            matches     = localMatchMedia(mql.media).matches;
+            timeoutID = setTimeout(function() {
+                for (var i = 0, il = queries.length; i < il; i++) {
+                    var mql         = queries[i].mql,
+                        listeners   = queries[i].listeners || [],
+                        matches     = localMatchMedia(mql.media).matches;
 
-                        // Update mql.matches value and call listeners
-                        // Fire listeners only if transitioning to or from matched state
-                        if (matches !== mql.matches) {
-                            mql.matches = matches;
+                    // Update mql.matches value and call listeners
+                    // Fire listeners only if transitioning to or from matched state
+                    if (matches !== mql.matches) {
+                        mql.matches = matches;
 
-                            for (var j = 0, jl = listeners.length; j < jl; j++) {
-                                listeners[j].call(window, mql);
-                            }
+                        for (var j = 0, jl = listeners.length; j < jl; j++) {
+                            listeners[j].call(window, mql);
                         }
                     }
-                }, 30);
-            };
+                }
+            }, 30);
+        };
 
-        window.matchMedia = function(media) {
-            var mql         = localMatchMedia(media),
-                listeners   = [],
-                index       = 0;
+    window.matchMedia = function(media) {
+        var mql         = localMatchMedia(media),
+            listeners   = [],
+            index       = 0;
 
-            mql.addListener = function(listener) {
-                // Changes would not occur to css media type so return now (Affects IE <= 8)
-                if (!hasMediaQueries) {
-                    return;
-                }
+        mql.addListener = function(listener) {
+            // Changes would not occur to css media type so return now (Affects IE <= 8)
+            if (!hasMediaQueries) {
+                return;
+            }
 
-                // Set up 'resize' listener for browsers that support CSS3 media queries (Not for IE <= 8)
-                // There should only ever be 1 resize listener running for performance
-                if (!isListening) {
-                    isListening = true;
-                    window.addEventListener('resize', handleChange, true);
-                }
+            // Set up 'resize' listener for browsers that support CSS3 media queries (Not for IE <= 8)
+            // There should only ever be 1 resize listener running for performance
+            if (!isListening) {
+                isListening = true;
+                window.addEventListener('resize', handleChange, true);
+            }
 
-                // Push object only if it has not been pushed already
-                if (index === 0) {
-                    index = queries.push({
-                        mql         : mql,
-                        listeners   : listeners
-                    });
-                }
+            // Push object only if it has not been pushed already
+            if (index === 0) {
+                index = queries.push({
+                    mql         : mql,
+                    listeners   : listeners
+                });
+            }
 
-                listeners.push(listener);
-            };
+            listeners.push(listener);
+        };
 
-            mql.removeListener = function(listener) {
-                for (var i = 0, il = listeners.length; i < il; i++){
-                    if (listeners[i] === listener){
-                        listeners.splice(i, 1);
-                    }
+        mql.removeListener = function(listener) {
+            for (var i = 0, il = listeners.length; i < il; i++){
+                if (listeners[i] === listener){
+                    listeners.splice(i, 1);
                 }
-            };
-
-            return mql;
+            }
         };
-    }
-}());
+
+        return mql;
+    };
+}());