diff --git a/lib/_debugger.js b/lib/_debugger.js
index b90d8fbe9c6..d60a3f5c369 100644
--- a/lib/_debugger.js
+++ b/lib/_debugger.js
@@ -209,6 +209,7 @@ Client.prototype._onResponse = function(res) {
       index = i;
       return true;
     }
+    return null;
   });
 
   var self = this;
@@ -259,7 +260,7 @@ Client.prototype.reqVersion = function(cb) {
   cb = cb || function () {};
   this.req({ command: 'version' } , function(err, body, res) {
     if (err) return cb(err);
-    cb(null, res.body.body.V8Version, res.body.running);
+    return cb(null, res.body.body.V8Version, res.body.running);
   });
 };
 
@@ -285,7 +286,7 @@ Client.prototype.reqLookup = function(refs, cb) {
       }
     }
 
-   cb(null, res);
+   return cb(null, res);
   });
 };
 
@@ -303,7 +304,7 @@ Client.prototype.reqScopes = function(cb) {
       return scope.object.ref;
     });
 
-    self.reqLookup(refs, function(err, res) {
+    return self.reqLookup(refs, function(err, res) {
       if (err) return cb(err);
 
       var globals = Object.keys(res).map(function(key) {
@@ -312,7 +313,7 @@ Client.prototype.reqScopes = function(cb) {
         });
       });
 
-      cb(null, globals.reverse());
+      return cb(null, globals.reverse());
     });
   });
 };
@@ -339,13 +340,13 @@ Client.prototype.reqEval = function(expression, cb) {
     var frame = bt.frames[self.currentFrame];
 
     var evalFrames = frame.scopes.map(function(s) {
-      if (!s) return;
+      if (!s) return null;
       var x = bt.frames[s.index];
-      if (!x) return;
+      if (!x) return null;
       return x.index;
     });
 
-    self._reqFramesEval(expression, evalFrames, cb);
+    return self._reqFramesEval(expression, evalFrames, cb);
   });
 };
 
@@ -364,7 +365,7 @@ Client.prototype._reqFramesEval = function(expression, evalFrames, cb) {
   cb = cb || function () {};
   this.reqFrameEval(expression, i, function(err, res) {
     if (!err) return cb(null, res);
-    self._reqFramesEval(expression, evalFrames, cb);
+    return self._reqFramesEval(expression, evalFrames, cb);
   });
 };
 
@@ -423,7 +424,7 @@ Client.prototype.reqScripts = function(cb) {
     for (var i = 0; i < res.length; i++) {
       self._addHandle(res[i]);
     }
-    cb(null);
+    return cb(null);
   });
 };
 
@@ -438,7 +439,7 @@ Client.prototype.listbreakpoints = function(cb) {
 };
 
 Client.prototype.setBreakpoint = function(req, cb) {
-  var req = {
+  req = {
     command: 'setbreakpoint',
     arguments: req
   };
@@ -447,7 +448,7 @@ Client.prototype.setBreakpoint = function(req, cb) {
 };
 
 Client.prototype.clearBreakpoint = function(req, cb) {
-  var req = {
+  req = {
     command: 'clearbreakpoint',
     arguments: req
   };
@@ -612,7 +613,7 @@ Client.prototype.fullTrace = function(cb) {
       refs.push(frame.receiver.ref);
     }
 
-    self.reqLookup(refs, function(err, res) {
+    return self.reqLookup(refs, function(err, res) {
       if (err) return cb(err);
 
       for (var i = 0; i < trace.frames.length; i++) {
@@ -622,7 +623,7 @@ Client.prototype.fullTrace = function(cb) {
         frame.receiver = res[frame.receiver.ref];
       }
 
-      cb(null, trace);
+      return cb(null, trace);
     });
   });
 };
diff --git a/lib/buffer.js b/lib/buffer.js
index 25dfaab042c..c1b07b635dd 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -988,13 +988,13 @@ Buffer.prototype.writeInt8 = function(value, offset, noAssert) {
     assert.ok(offset < buffer.length,
         'Trying to write beyond buffer length');
 
-    verifsint(value, 0x7f, -0xf0);
+    verifsint(value, 127, -240);
   }
 
   if (value >= 0) {
     buffer.writeUInt8(value, offset, noAssert);
   } else {
-    buffer.writeUInt8(0xff + value + 1, offset, noAssert);
+    buffer.writeUInt8(255 + value + 1, offset, noAssert);
   }
 };
 
@@ -1012,13 +1012,13 @@ function writeInt16(buffer, value, offset, isBigEndian, noAssert) {
     assert.ok(offset + 1 < buffer.length,
         'Trying to write beyond buffer length');
 
-    verifsint(value, 0x7fff, -0xf000);
+    verifsint(value, 32767, -61440);
   }
 
   if (value >= 0) {
     writeUInt16(buffer, value, offset, isBigEndian, noAssert);
   } else {
-    writeUInt16(buffer, 0xffff + value + 1, offset, isBigEndian, noAssert);
+    writeUInt16(buffer, 65535 + value + 1, offset, isBigEndian, noAssert);
   }
 }
 
@@ -1044,13 +1044,13 @@ function writeInt32(buffer, value, offset, isBigEndian, noAssert) {
     assert.ok(offset + 3 < buffer.length,
         'Trying to write beyond buffer length');
 
-    verifsint(value, 0x7fffffff, -0xf0000000);
+    verifsint(value, 2147483647, -4026531840);
   }
 
   if (value >= 0) {
     writeUInt32(buffer, value, offset, isBigEndian, noAssert);
   } else {
-    writeUInt32(buffer, 0xffffffff + value + 1, offset, isBigEndian, noAssert);
+    writeUInt32(buffer, 2147483647 + value + 1, offset, isBigEndian, noAssert);
   }
 }
 
@@ -1079,8 +1079,7 @@ function writeFloat(buffer, value, offset, isBigEndian, noAssert) {
     verifIEEE754(value, 3.4028234663852886e+38, -3.4028234663852886e+38);
   }
 
-  require('buffer_ieee754').writeIEEE754(buffer, value, offset, isBigEndian,
-      23, 4);
+  require('buffer_ieee754').writeIEEE754(buffer, value, offset, isBigEndian, 23, 4);
 }
 
 Buffer.prototype.writeFloatLE = function(value, offset, noAssert) {
diff --git a/lib/buffer_ieee754.js b/lib/buffer_ieee754.js
index 7a86b2f2948..fcdefe435f8 100644
--- a/lib/buffer_ieee754.js
+++ b/lib/buffer_ieee754.js
@@ -37,29 +37,23 @@ exports.readIEEE754 = function(buffer, offset, isBE, mLen, nBytes) {
       eBias = eMax >> 1,
       nBits = -7,
       i = isBE ? 0 : (nBytes - 1),
-      d = isBE ? 1 : -1,
       s = buffer[offset + i];
 
-  i += d;
+  i += d = isBE ? 1 : -1;
 
-  e = s & ((1 << (-nBits)) - 1);
-  s >>= (-nBits);
+  e = s & (1 << -nBits) - 1;
+  s >>= -nBits;
   nBits += eLen;
   for (; nBits > 0; e = e * 256 + buffer[offset + i], i += d, nBits -= 8);
 
-  m = e & ((1 << (-nBits)) - 1);
-  e >>= (-nBits);
+  m = e & (1 << -nBits) - 1;
+  e >>= -nBits;
   nBits += mLen;
   for (; nBits > 0; m = m * 256 + buffer[offset + i], i += d, nBits -= 8);
 
-  if (e === 0) {
-    e = 1 - eBias;
-  } else if (e === eMax) {
-    return m ? NaN : ((s ? -1 : 1) * Infinity);
-  } else {
-    m = m + Math.pow(2, mLen);
-    e = e - eBias;
-  }
+  if (e === 0) e = 1 - eBias;
+  else if (e === eMax) return m ? NaN : (s ? -1 : 1) * Infinity;
+  else m = m + Math.pow(2, mLen), e = e - eBias;
   return (s ? -1 : 1) * m * Math.pow(2, e - mLen);
 };
 
@@ -75,42 +69,17 @@ exports.writeIEEE754 = function(buffer, value, offset, isBE, mLen, nBytes) {
 
   value = Math.abs(value);
 
-  if (isNaN(value) || value === Infinity) {
-    m = isNaN(value) ? 1 : 0;
-    e = eMax;
-  } else {
+  if (isNaN(value) || value === Infinity) m = isNaN(value) ? 1 : 0, e = eMax;
+  else {
     e = Math.floor(Math.log(value) / Math.LN2);
-    if (value * (c = Math.pow(2, -e)) < 1) {
-      e--;
-      c *= 2;
-    }
-    if (e+eBias >= 1) {
-      value += rt / c;
-    } else {
-      value += rt * Math.pow(2, 1 - eBias);
-    }
-    if (value * c >= 2) {
-      e++;
-      c /= 2;
-    }
-
-    if (e + eBias >= eMax) {
-      m = 0;
-      e = eMax;
-    } else if (e + eBias >= 1) {
-      m = (value * c - 1) * Math.pow(2, mLen);
-      e = e + eBias;
-    } else {
-      m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen);
-      e = 0;
-    }
+    if (value * (c = Math.pow(2, -e)) < 1) e--, c *= 2;
+    value += e + eBias >= 1 ? rt / c : rt * Math.pow(2, 1 - eBias);
+    value * c >= 2 && ( e++, c /= 2 );
+    e + eBias >= eMax ? ( m = 0, e = eMax ) : e + eBias >= 1 ? ( m = (value * c - 1) * Math.pow(2, mLen), e = e + eBias) : (m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen), e = 0 );
   }
 
-  for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8);
-
+  for (; mLen >= 8; buffer[offset + i] = m & 256, i += d, m /= 256, mLen -= 8);
   e = (e << mLen) | m;
-  eLen += mLen;
-  for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8);
-
+  for (eLen += mLen; eLen > 0; buffer[offset + i] = e & 256, i += d, e /= 256, eLen -= 8);
   buffer[offset + i - d] |= s * 128;
 };
diff --git a/lib/child_process_legacy.js b/lib/child_process_legacy.js
index edcbaa0a73c..0da58269663 100644
--- a/lib/child_process_legacy.js
+++ b/lib/child_process_legacy.js
@@ -181,18 +181,12 @@ exports.execFile = function(file /* args, options, callback */) {
 
   child.stdout.addListener('data', function(chunk) {
     stdout += chunk;
-    if (stdout.length > options.maxBuffer) {
-      err = new Error('maxBuffer exceeded.');
-      kill();
-    }
+    ( stdout.length > options.maxBuffer ) && (err = new Error('maxBuffer exceeded.'), kill());
   });
 
   child.stderr.addListener('data', function(chunk) {
     stderr += chunk;
-    if (stderr.length > options.maxBuffer) {
-      err = new Error('maxBuffer exceeded.');
-      kill();
-    }
+    ( stderr.length > options.maxBuffer ) && ( err = new Error('maxBuffer exceeded.'), kill() );
   });
 
   child.addListener('exit', exithandler);
@@ -266,27 +260,9 @@ ChildProcess.prototype.spawn = function(path, args, options, customFds) {
   args = args || [];
 
   var cwd, env, setsid, uid, gid;
-  if (!options || options.cwd === undefined &&
-      options.env === undefined &&
-      options.customFds === undefined &&
-      options.gid === undefined &&
-      options.uid === undefined) {
-    // Deprecated API: (path, args, options, env, customFds)
-    cwd = '';
-    env = options || process.env;
-    customFds = customFds || [-1, -1, -1];
-    setsid = false;
-    uid = -1;
-    gid = -1;
-  } else {
-    // Recommended API: (path, args, options)
-    cwd = options.cwd || '';
-    env = options.env || process.env;
-    customFds = options.customFds || [-1, -1, -1];
-    setsid = options.setsid ? true : false;
-    uid = options.hasOwnProperty('uid') ? options.uid : -1;
-    gid = options.hasOwnProperty('gid') ? options.gid : -1;
-  }
+  !options || options.cwd === void 0 && options.env === void 0 && options.customFds === void 0 && options.gid === void 0 && options.uid === void 0 ?
+    ( cwd = '', env = options || process.env, customFds = customFds || [-1, -1, -1], setsid = false, uid = -1, gid = -1 ) : // Deprecated API: (path, args, options, env, customFds)
+    (cwd = options.cwd || '', env = options.env || process.env, customFds = options.customFds || [-1, -1, -1], setsid = options.setsid ? true : false, uid = options.hasOwnProperty('uid') ? options.uid : -1, gid = options.hasOwnProperty('gid') ? options.gid : -1); // Recommended API: (path, args, options)
 
   var envPairs = [];
   var keys = Object.keys(env);
@@ -310,7 +286,7 @@ ChildProcess.prototype.spawn = function(path, args, options, customFds) {
                                  gid);
   this.fds = fds;
 
-  if (customFds[0] === -1 || customFds[0] === undefined) {
+  if (customFds[0] === -1 || customFds[0] === void 0) {
     this.stdin.open(fds[0]);
     this.stdin.writable = true;
     this.stdin.readable = false;
@@ -318,7 +294,7 @@ ChildProcess.prototype.spawn = function(path, args, options, customFds) {
     this.stdin = null;
   }
 
-  if (customFds[1] === -1 || customFds[1] === undefined) {
+  if (customFds[1] === -1 || customFds[1] === void 0) {
     this.stdout.open(fds[1]);
     this.stdout.writable = false;
     this.stdout.readable = true;
@@ -327,7 +303,7 @@ ChildProcess.prototype.spawn = function(path, args, options, customFds) {
     this.stdout = null;
   }
 
-  if (customFds[2] === -1 || customFds[2] === undefined) {
+  if (customFds[2] === -1 || customFds[2] === void 0) {
     this.stderr.open(fds[2]);
     this.stderr.writable = false;
     this.stderr.readable = true;
diff --git a/lib/fs.js b/lib/fs.js
index 60b2930f2a0..294c52534ed 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -105,7 +105,7 @@ fs.readFile = function(path, encoding_) {
         return callback(er);
       }
     }
-    callback(null, buffer);
+    return callback(null, buffer);
   });
 };
 
@@ -411,8 +411,7 @@ fs.readlinkSync = function(path) {
 
 fs.symlink = function(destination, path, mode_, callback) {
   var mode = (typeof(mode_) == 'string' ? mode_ : null);
-  var callback_ = arguments[arguments.length - 1];
-  var callback = (typeof(callback_) == 'function' ? callback_ : null);
+  callback = (typeof(callback) == 'function' ? callback : null);
   binding.symlink(destination, path, mode, callback);
 };
 
@@ -563,8 +562,7 @@ function writeAll(fd, buffer, offset, length, callback) {
 
 fs.writeFile = function(path, data, encoding_, callback) {
   var encoding = (typeof(encoding_) == 'string' ? encoding_ : 'utf8');
-  var callback_ = arguments[arguments.length - 1];
-  var callback = (typeof(callback_) == 'function' ? callback_ : null);
+  callback = (typeof(callback) == 'function' ? callback : null);
   fs.open(path, 'w', 0666, function(openErr, fd) {
     if (openErr) {
       if (callback) callback(openErr);
@@ -746,7 +744,7 @@ if (isWindows) {
 
   // windows version
   fs.realpathSync = function realpathSync(p, cache) {
-    var p = path.resolve(p);
+    p = path.resolve(p);
     if (cache && Object.prototype.hasOwnProperty.call(cache, p)) {
       return cache[p];
     }
@@ -761,7 +759,7 @@ if (isWindows) {
       cb = cache;
       cache = null;
     }
-    var p = path.resolve(p);
+    p = path.resolve(p);
     if (cache && Object.prototype.hasOwnProperty.call(cache, p)) {
       return cb(null, cache[p]);
     }
@@ -770,6 +768,7 @@ if (isWindows) {
       if (cache) cache[p] = p;
       cb(null, p);
     });
+    return null;
   };
 
 
@@ -933,7 +932,9 @@ if (isWindows) {
         fs.readlink(base, function(err, target) {
           gotTarget(err, seenLinks[id] = target);
         });
+        return null;
       });
+      return null;
     }
 
     function gotTarget(err, target, base) {
@@ -941,7 +942,7 @@ if (isWindows) {
 
       var resolvedLink = path.resolve(previous, target);
       if (cache) cache[base] = resolvedLink;
-      gotResolvedLink(resolvedLink);
+      return gotResolvedLink(resolvedLink);
     }
 
     function gotResolvedLink(resolvedLink) {
@@ -953,6 +954,7 @@ if (isWindows) {
 
       return process.nextTick(LOOP);
     }
+    return null;
   };
 
 }
@@ -1011,7 +1013,7 @@ var ReadStream = fs.ReadStream = function(path, options) {
   }
 
   if (this.fd !== null) {
-    return;
+    return null;
   }
 
   fs.open(this.path, this.flags, this.mode, function(err, fd) {
@@ -1025,6 +1027,7 @@ var ReadStream = fs.ReadStream = function(path, options) {
     self.emit('open', fd);
     self._read();
   });
+  return null;
 };
 util.inherits(ReadStream, Stream);
 
@@ -1335,3 +1338,4 @@ WriteStream.prototype.destroy = function(cb) {
 // There is no shutdown() for files.
 WriteStream.prototype.destroySoon = WriteStream.prototype.end;
 
+
diff --git a/lib/http.js b/lib/http.js
index efa0963be33..aa3e94036ad 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -604,7 +604,7 @@ OutgoingMessage.prototype.write = function(chunk, encoding) {
   if (this.chunkedEncoding) {
     if (typeof(chunk) === 'string') {
       len = Buffer.byteLength(chunk, encoding);
-      var chunk = len.toString(16) + CRLF + chunk + CRLF;
+      chunk = len.toString(16) + CRLF + chunk + CRLF;
       ret = this._send(chunk, encoding);
     } else {
       // buffer
@@ -1726,7 +1726,7 @@ exports.cat = function(url, encoding_, headers_) {
     }
   }
 
-  var url = require('url').parse(url);
+  url = require('url').parse(url);
 
   var hasHost = false;
   if (Array.isArray(headers)) {
diff --git a/lib/http2.js b/lib/http2.js
index a42a613c133..755f94b95c8 100644
--- a/lib/http2.js
+++ b/lib/http2.js
@@ -604,7 +604,7 @@ OutgoingMessage.prototype.write = function(chunk, encoding) {
   if (this.chunkedEncoding) {
     if (typeof(chunk) === 'string') {
       len = Buffer.byteLength(chunk, encoding);
-      var chunk = len.toString(16) + CRLF + chunk + CRLF;
+      chunk = len.toString(16) + CRLF + chunk + CRLF;
       ret = this._send(chunk, encoding);
     } else {
       // buffer
diff --git a/lib/readline.js b/lib/readline.js
index 21422581096..66884aa1430 100644
--- a/lib/readline.js
+++ b/lib/readline.js
@@ -105,6 +105,7 @@ function Interface(input, output, completer) {
       });
     }
   }
+  return null;
 }
 
 inherits(Interface, EventEmitter);
@@ -316,7 +317,7 @@ Interface.prototype._tabComplete = function() {
 
         // If there is a common prefix to all matches, then apply that
         // portion.
-        var f = completions.filter(function(e) { if (e) return e; });
+        var f = completions.filter(function(e) { return !!e; });
         var prefix = commonPrefix(f);
         if (prefix.length > completeOn.length) {
           self._insertString(prefix.slice(completeOn.length));
diff --git a/lib/repl.js b/lib/repl.js
index de380929f50..91ad07b6960 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -183,6 +183,7 @@ function REPLServer(prompt, stream, eval) {
         } else {
           finish(null, ret);
         }
+        return null;
       });
 
     } else {
diff --git a/lib/tls.js b/lib/tls.js
index 6f26ffb4551..82b53b73d4c 100644
--- a/lib/tls.js
+++ b/lib/tls.js
@@ -916,6 +916,7 @@ Server.prototype.SNICallback = function(servername) {
       ctx = elem[1];
       return true;
     }
+    return null;
   });
 
   return ctx;
diff --git a/lib/zlib.js b/lib/zlib.js
index 43725bff2d2..7ee7d2bee61 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -93,12 +93,12 @@ exports.createUnzip = function(o) {
 // minimal 2-byte header
 function Deflate(opts) {
   if (!(this instanceof Deflate)) return new Deflate(opts);
-  Zlib.call(this, opts, binding.Deflate);
+  return Zlib.call(this, opts, binding.Deflate);
 }
 
 function Inflate(opts) {
   if (!(this instanceof Inflate)) return new Inflate(opts);
-  Zlib.call(this, opts, binding.Inflate);
+  return Zlib.call(this, opts, binding.Inflate);
 }
 
 
@@ -106,12 +106,12 @@ function Inflate(opts) {
 // gzip - bigger header, same deflate compression
 function Gzip(opts) {
   if (!(this instanceof Gzip)) return new Gzip(opts);
-  Zlib.call(this, opts, binding.Gzip);
+  return Zlib.call(this, opts, binding.Gzip);
 }
 
 function Gunzip(opts) {
   if (!(this instanceof Gunzip)) return new Gunzip(opts);
-  Zlib.call(this, opts, binding.Gunzip);
+  return Zlib.call(this, opts, binding.Gunzip);
 }
 
 
@@ -119,19 +119,19 @@ function Gunzip(opts) {
 // raw - no header
 function DeflateRaw(opts) {
   if (!(this instanceof DeflateRaw)) return new DeflateRaw(opts);
-  Zlib.call(this, opts, binding.DeflateRaw);
+  return Zlib.call(this, opts, binding.DeflateRaw);
 }
 
 function InflateRaw(opts) {
   if (!(this instanceof InflateRaw)) return new InflateRaw(opts);
-  Zlib.call(this, opts, binding.InflateRaw);
+  return Zlib.call(this, opts, binding.InflateRaw);
 }
 
 
 // auto-detect header.
 function Unzip(opts) {
   if (!(this instanceof Unzip)) return new Unzip(opts);
-  Zlib.call(this, opts, binding.Unzip);
+  return Zlib.call(this, opts, binding.Unzip);
 }