http: use strict comparison

PR-URL: nodejs#17011
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

lib/_http_client.js

@@ -44,7 +44,7 @@ const errors = require('internal/errors');
 const INVALID_PATH_REGEX = /[^\u0021-\u00ff]/;
 
 function validateHost(host, name) {
-  if (host != null && typeof host !== 'string') {
+  if (host !== null && host !== undefined && typeof host !== 'string') {
     throw new errors.TypeError('ERR_INVALID_ARG_TYPE', `options.${name}`,
                                ['string', 'undefined', 'null'], host);
   }
@@ -113,7 +113,7 @@ function ClientRequest(options, cb) {
 
   var method = options.method;
   var methodIsString = (typeof method === 'string');
-  if (method != null && !methodIsString) {
+  if (method !== null && method !== undefined && !methodIsString) {
     throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'method',
                                'string', method);
   }