diff --git a/lib/buffer.js b/lib/buffer.js
index 8c16f07acebc5b..61ac7776d5cf52 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -505,41 +505,29 @@ function byteLength(string, encoding) {
     return (mustMatch ? -1 : byteLengthUtf8(string));
 
   encoding += '';
+  encoding = encoding.toLowerCase();
   switch (encoding.length) {
     case 4:
-      if (encoding === 'utf8') return byteLengthUtf8(string);
-      if (encoding === 'ucs2') return len * 2;
-      encoding = encoding.toLowerCase();
       if (encoding === 'utf8') return byteLengthUtf8(string);
       if (encoding === 'ucs2') return len * 2;
       break;
     case 5:
-      if (encoding === 'utf-8') return byteLengthUtf8(string);
-      if (encoding === 'ascii') return len;
-      if (encoding === 'ucs-2') return len * 2;
-      encoding = encoding.toLowerCase();
       if (encoding === 'utf-8') return byteLengthUtf8(string);
       if (encoding === 'ascii') return len;
       if (encoding === 'ucs-2') return len * 2;
       break;
     case 7:
-      if (encoding === 'utf16le' || encoding.toLowerCase() === 'utf16le')
-        return len * 2;
+      if (encoding === 'utf16le') return len * 2;
       break;
     case 8:
-      if (encoding === 'utf-16le' || encoding.toLowerCase() === 'utf-16le')
-        return len * 2;
+      if (encoding === 'utf-16le') return len * 2;
       break;
     case 6:
-      if (encoding === 'latin1' || encoding === 'binary') return len;
-      if (encoding === 'base64') return base64ByteLength(string, len);
-      encoding = encoding.toLowerCase();
       if (encoding === 'latin1' || encoding === 'binary') return len;
       if (encoding === 'base64') return base64ByteLength(string, len);
       break;
     case 3:
-      if (encoding === 'hex' || encoding.toLowerCase() === 'hex')
-        return len >>> 1;
+      if (encoding === 'hex') return len >>> 1;
       break;
   }
   return (mustMatch ? -1 : byteLengthUtf8(string));
@@ -568,43 +556,30 @@ Object.defineProperty(Buffer.prototype, 'offset', {
 function stringSlice(buf, encoding, start, end) {
   if (encoding === undefined) return buf.utf8Slice(start, end);
   encoding += '';
+  encoding = encoding.toLowerCase();
   switch (encoding.length) {
     case 4:
-      if (encoding === 'utf8') return buf.utf8Slice(start, end);
-      if (encoding === 'ucs2') return buf.ucs2Slice(start, end);
-      encoding = encoding.toLowerCase();
       if (encoding === 'utf8') return buf.utf8Slice(start, end);
       if (encoding === 'ucs2') return buf.ucs2Slice(start, end);
       break;
     case 5:
-      if (encoding === 'utf-8') return buf.utf8Slice(start, end);
-      if (encoding === 'ascii') return buf.asciiSlice(start, end);
-      if (encoding === 'ucs-2') return buf.ucs2Slice(start, end);
-      encoding = encoding.toLowerCase();
       if (encoding === 'utf-8') return buf.utf8Slice(start, end);
       if (encoding === 'ascii') return buf.asciiSlice(start, end);
       if (encoding === 'ucs-2') return buf.ucs2Slice(start, end);
       break;
     case 6:
-      if (encoding === 'latin1' || encoding === 'binary')
-        return buf.latin1Slice(start, end);
-      if (encoding === 'base64') return buf.base64Slice(start, end);
-      encoding = encoding.toLowerCase();
       if (encoding === 'latin1' || encoding === 'binary')
         return buf.latin1Slice(start, end);
       if (encoding === 'base64') return buf.base64Slice(start, end);
       break;
     case 3:
-      if (encoding === 'hex' || encoding.toLowerCase() === 'hex')
-        return buf.hexSlice(start, end);
+      if (encoding === 'hex') return buf.hexSlice(start, end);
       break;
     case 7:
-      if (encoding === 'utf16le' || encoding.toLowerCase() === 'utf16le')
-        return buf.ucs2Slice(start, end);
+      if (encoding === 'utf16le') return buf.ucs2Slice(start, end);
       break;
     case 8:
-      if (encoding === 'utf-16le' || encoding.toLowerCase() === 'utf-16le')
-        return buf.ucs2Slice(start, end);
+      if (encoding === 'utf-16le') return buf.ucs2Slice(start, end);
       break;
   }
   throw new ERR_UNKNOWN_ENCODING(encoding);
@@ -914,45 +889,32 @@ Buffer.prototype.write = function write(string, offset, length, encoding) {
     return this.utf8Write(string, offset, length);
 
   encoding += '';
+  encoding = encoding.toLowerCase();
   switch (encoding.length) {
     case 4:
-      if (encoding === 'utf8') return this.utf8Write(string, offset, length);
-      if (encoding === 'ucs2') return this.ucs2Write(string, offset, length);
-      encoding = encoding.toLowerCase();
       if (encoding === 'utf8') return this.utf8Write(string, offset, length);
       if (encoding === 'ucs2') return this.ucs2Write(string, offset, length);
       break;
     case 5:
-      if (encoding === 'utf-8') return this.utf8Write(string, offset, length);
-      if (encoding === 'ascii') return this.asciiWrite(string, offset, length);
-      if (encoding === 'ucs-2') return this.ucs2Write(string, offset, length);
-      encoding = encoding.toLowerCase();
       if (encoding === 'utf-8') return this.utf8Write(string, offset, length);
       if (encoding === 'ascii') return this.asciiWrite(string, offset, length);
       if (encoding === 'ucs-2') return this.ucs2Write(string, offset, length);
       break;
     case 7:
-      if (encoding === 'utf16le' || encoding.toLowerCase() === 'utf16le')
-        return this.ucs2Write(string, offset, length);
+      if (encoding === 'utf16le') return this.ucs2Write(string, offset, length);
       break;
     case 8:
-      if (encoding === 'utf-16le' || encoding.toLowerCase() === 'utf-16le')
+      if (encoding === 'utf-16le')
         return this.ucs2Write(string, offset, length);
       break;
     case 6:
-      if (encoding === 'latin1' || encoding === 'binary')
-        return this.latin1Write(string, offset, length);
-      if (encoding === 'base64')
-        return this.base64Write(string, offset, length);
-      encoding = encoding.toLowerCase();
       if (encoding === 'latin1' || encoding === 'binary')
         return this.latin1Write(string, offset, length);
       if (encoding === 'base64')
         return this.base64Write(string, offset, length);
       break;
     case 3:
-      if (encoding === 'hex' || encoding.toLowerCase() === 'hex')
-        return this.hexWrite(string, offset, length);
+      if (encoding === 'hex') return this.hexWrite(string, offset, length);
       break;
   }
   throw new ERR_UNKNOWN_ENCODING(encoding);