diff --git a/lib/callbacks.js b/lib/callbacks.js
index eb1c30a5..a7a20082 100644
--- a/lib/callbacks.js
+++ b/lib/callbacks.js
@@ -65,26 +65,29 @@ exports.listCallbacks = function (config, options, callback) {
     throw (new errors.ArgumentError('No callback given to listCallbacks'));
   }
   api(config, 'GET', '/callback', null, function (err, response, body) {
-    if (!err && body && body.constructor === String) {
-      try {
-        body = JSON.parse(body);
-      }
-      catch (_err) {
-        err = _err;
-      }
+    if (err) {
+      callback(err);
     }
-    if (err || Math.floor(response.statusCode / 100) !== 2) {
-      if (response && response.statusCode === 403) {
+
+    try {
+      body = JSON.parse(body);
+    }
+    catch (_err) {
+      err = _err;
+    }
+
+    switch (response.statusCode) {
+      case 200:
+        callback(null, body.map(function (item) {
+          return new Callback(config, item);
+        }));
+        return;
+      case 403:
         callback(new errors.AuthError('Invalid API key or secret'));
-      }
-      else {
+        return;
+      default:
         callback(new errors.RequestError('Unexpected response from OpenTok: ' + JSON.stringify(body || { statusCode: response.statusCode, statusMessage: response.statusMessage })));
-      }
-    }
-    else {
-      callback(null, body.map(function (item) {
-        return new Callback(config, item);
-      }));
+        return;
     }
   });
 };
@@ -104,20 +107,21 @@ exports.registerCallback = function (config, options, callback) {
   }, function apiCallback(err, response, body) {
     if (err) {
       callback(err);
+      return;
     }
-    else if (Math.floor(response.statusCode / 100) !== 2) {
-      if (response && response.statusCode === 404) {
+
+    switch(response.statusCode) {
+      case 200:
+        callback(null, new Callback(config, body));
+        return;
+      case 404:
         callback(new errors.CallbackError('Callback event not found'));
-      }
-      else if (response && response.statusCode === 403) {
+        return;
+      case 403:
         callback(new errors.AuthError('Invalid API key or secret'));
-      }
-      else {
+        return;
+      default:
         callback(new errors.RequestError('Unexpected response from OpenTok: ' + JSON.stringify(body || { statusCode: response.statusCode, statusMessage: response.statusMessage })));
-      }
-    }
-    else {
-      callback(null, new Callback(config, body));
     }
   });
 };
@@ -138,20 +142,24 @@ exports.unregisterCallback = function (config, callbackId, callback) {
     function (err, response, body) {
       if (err) {
         callback(err);
+        return;
       }
-      else if (Math.floor(response.statusCode / 100) !== 2) {
-        if (response && response.statusCode === 404) {
+
+      switch (response.statusCode) {
+        case 204:
+          callback(null);
+          return;
+        case 404:
           callback(new errors.CallbackError('Callback not found'));
-        }
-        else if (response && response.statusCode === 403) {
+          return;
+        case 403:
           callback(new errors.AuthError('Invalid API key or secret'));
-        }
-        else {
-          callback(new errors.RequestError('Unexpected response from OpenTok: ' + JSON.stringify(body || { statusCode: response.statusCode, statusMessage: response.statusMessage })));
-        }
-      }
-      else {
-        callback(null);
+          return;
+        default:
+          callback(new errors.RequestError('Unexpected response from OpenTok: ' + JSON.stringify(body || {
+            statusCode: response.statusCode,
+            statusMessage: response.statusMessage
+          })));
       }
     }
   );
diff --git a/lib/moderation.js b/lib/moderation.js
index e27bd1ff..71d5af02 100644
--- a/lib/moderation.js
+++ b/lib/moderation.js
@@ -15,7 +15,7 @@ var api = function (config, method, session, connection, body, callback)  {
         (config.uaAddendum ? ' ' + config.uaAddendum : '')
     };
 
-  if (body && ['POST', 'PATCH', 'PUT'].includes(method)) {
+  if (body) {
     headers['Content-Type'] = 'application/json';
   }
 
@@ -37,6 +37,7 @@ var api = function (config, method, session, connection, body, callback)  {
       callback(null, otResponse, body);
     })
     .catch(async (error) => {
+      /* istanbul ignore next */
       callback(error);
     });
 };
diff --git a/lib/opentok.js b/lib/opentok.js
index 08ff22b7..5dfa4d52 100644
--- a/lib/opentok.js
+++ b/lib/opentok.js
@@ -36,9 +36,7 @@ function decodeSessionId(sessionId) {
   if (typeof Buffer.from === 'function') {
     sessionId = Buffer.from(sessionId, 'base64').toString('ascii');
   }
-  else {
-    sessionId = Buffer.from(sessionId, 'base64').toString('ascii');
-  }
+
   // separate fields
   fields = sessionId.split('~');
   return {
@@ -1158,7 +1156,7 @@ OpenTok = function (apiKey, apiSecret, env) {
   * an <code>error</code> object is passed in as the first parameter of the function.
   * Upon success, the function is called with no error object passed in (as the first parameter)
   * and the second parameter is an object with the following properties:
-  * 
+  *
   *   <ul>
   *     <li>
   *       <code>id</code> -- A unique ID identifying the Audio Streamer WebSocket connection.
@@ -1168,7 +1166,7 @@ OpenTok = function (apiKey, apiSecret, env) {
   *       WebSocket connection in the OpenTok session.
   *     </li>
   *   </ul>
-  * 
+  *
   * @method #websocketConnect
   * @memberof OpenTok
   */
@@ -1825,7 +1823,7 @@ OpenTok.prototype.dial = function (sessionId, token, sipUri, options, callback)
  * OpenTok network. If you do not set a location hint, the OpenTok servers will be based on
  * the first client connecting to the session.
  * </li>
- * 
+ *
  *     <li><code>e2ee</code> (Boolean) &mdash;
  * Determines whether to enable <a href="https://tokbox.com/developer/guides/end-to-end-encryption/">
 `end-to-end encryption</a>