diff --git a/crypto.js b/crypto.js
index 4aaca9520..bfffa1f44 100644
--- a/crypto.js
+++ b/crypto.js
@@ -569,6 +569,7 @@ var CipherTransformFactory = (function() {
       };
     }
     error('Unknown crypto method');
+    return null;
   }
 
   constructor.prototype = {
diff --git a/fonts.js b/fonts.js
index 50701cbca..3e3eece81 100755
--- a/fonts.js
+++ b/fonts.js
@@ -66,7 +66,7 @@ var FontMeasure = (function FontMeasure() {
 
   return {
     setActive: function fonts_setActive(font, size) {
-      if (current = font) {
+      if (current == font) {
         var sizes = current.sizes;
         if (!(measureCache = sizes[size]))
           measureCache = sizes[size] = Object.create(null);
@@ -856,7 +856,7 @@ var Font = (function Font() {
           var language = int16(font.getBytes(2));
 
           if (format == 4) {
-            return;
+            return cmap.data;
           } else if (format == 0) {
             // Characters below 0x20 are controls characters that are hardcoded
             // into the platform so if some characters in the font are assigned
@@ -927,6 +927,7 @@ var Font = (function Font() {
             return cmap.data = createCMapTable(glyphs);
           }
         }
+        return cmap.data;
       };
 
       // Check that required tables are present
@@ -2287,7 +2288,7 @@ var Type2CFF = (function() {
             id = (id << 8) | bytes[pos++];
             charset.push(strings[id]);
           }
-          return charset;
+          break;
         case 1:
           while (charset.length <= length) {
             var first = bytes[pos++];
@@ -2296,7 +2297,7 @@ var Type2CFF = (function() {
             for (var i = 0; i <= numLeft; ++i)
               charset.push(strings[first++]);
           }
-          return charset;
+          break;
         case 2:
           while (charset.length <= length) {
             var first = bytes[pos++];
@@ -2306,11 +2307,11 @@ var Type2CFF = (function() {
             for (var i = 0; i <= numLeft; ++i)
               charset.push(strings[first++]);
           }
-          return charset;
+          break;
         default:
           error('Unknown charset format');
       }
-
+      return charset;
     },
     getPrivDict: function cff_getprivdict(baseDict, strings) {
       var dict = {};
@@ -2440,6 +2441,7 @@ var Type2CFF = (function() {
         } else {
           error('Incorrect byte');
         }
+        return -1;
       };
 
       function parseFloatOperand() {
diff --git a/pdf.js b/pdf.js
index 41cd6d07e..d97588c2c 100644
--- a/pdf.js
+++ b/pdf.js
@@ -2093,7 +2093,7 @@ var LZWStream = (function() {
       var c = this.str.getByte();
       if (c == null) {
         this.eof = true;
-        return;
+        return null;
       }
       cachedData = (cachedData << 8) | c;
       bitsCached += 8;
@@ -5208,7 +5208,7 @@ var Util = (function() {
     return 'rgb(' + ri + ',' + gi + ',' + bi + ')';
   };
   constructor.makeCssCmyk = function makecmyk(c, m, y, k) {
-    var c = (new DeviceCmykCS()).getRgb([c, m, y, k]);
+    c = (new DeviceCmykCS()).getRgb([c, m, y, k]);
     var ri = (255 * c[0]) | 0, gi = (255 * c[1]) | 0, bi = (255 * c[2]) | 0;
     return 'rgb(' + ri + ',' + gi + ',' + bi + ')';
   };
@@ -5335,6 +5335,7 @@ var ColorSpace = (function() {
     } else {
       error('unrecognized color space object: "' + cs + '"');
     }
+    return null;
   };
 
   return constructor;
@@ -5623,6 +5624,7 @@ var Pattern = (function() {
     default:
       error('Unknown type of pattern: ' + typeNum);
     }
+    return null;
   };
 
   constructor.parseShading = function pattern_shading(shading, matrix,
diff --git a/web/viewer.js b/web/viewer.js
index c93df3b74..1e016e6e9 100644
--- a/web/viewer.js
+++ b/web/viewer.js
@@ -417,16 +417,18 @@ window.addEventListener('transitionend', function(evt) {
   var pagesCount = PDFView.pages.length;
 
   var container = document.getElementById('sidebarView');
-  container._interval = window.setInterval(function() {
-    if (pageIndex >= pagesCount)
-      return window.clearInterval(container._interval);
+  container._interval = window.setInterval(function interval() {
+    if (pageIndex >= pagesCount) {
+      window.clearInterval(container._interval);
+      return;
+    }
 
     PDFView.thumbnails[pageIndex++].draw();
   }, 500);
 }, true);
 
 
-window.addEventListener('scalechange', function(evt) {
+window.addEventListener('scalechange', function scalechange(evt) {
   var options = document.getElementById('scaleSelect').options;
   for (var i = 0; i < options.length; i++) {
     var option = options[i];
@@ -434,7 +436,7 @@ window.addEventListener('scalechange', function(evt) {
   }
 }, true);
 
-window.addEventListener('pagechange', function(evt) {
+window.addEventListener('pagechange', function pagechange(evt) {
   var page = evt.detail;
   document.location.hash = page;
   document.getElementById('pageNumber').value = page;