lib: use destructuring for some constants

This change is to unify the declaration for constants into using
destructuring on the top-level-module scope, reducing some redundant
code.

PR-URL: https://github.com/nodejs/node/pull/16063
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

lib/_http_server.js

@@ -23,17 +23,19 @@
 
 const util = require('util');
 const net = require('net');
-const HTTPParser = process.binding('http_parser').HTTPParser;
+const { HTTPParser } = process.binding('http_parser');
 const assert = require('assert').ok;
-const common = require('_http_common');
-const parsers = common.parsers;
-const freeParser = common.freeParser;
-const debug = common.debug;
-const CRLF = common.CRLF;
-const continueExpression = common.continueExpression;
-const chunkExpression = common.chunkExpression;
-const httpSocketSetup = common.httpSocketSetup;
-const OutgoingMessage = require('_http_outgoing').OutgoingMessage;
+const {
+  parsers,
+  freeParser,
+  debug,
+  CRLF,
+  continueExpression,
+  chunkExpression,
+  httpSocketSetup,
+  _checkInvalidHeaderChar: checkInvalidHeaderChar
+} = require('_http_common');
+const { OutgoingMessage } = require('_http_outgoing');
 const { outHeadersKey, ondrain } = require('internal/http');
 const errors = require('internal/errors');
 
@@ -223,7 +225,7 @@ function writeHead(statusCode, reason, obj) {
     headers = obj;
   }
 
-  if (common._checkInvalidHeaderChar(this.statusMessage))
+  if (checkInvalidHeaderChar(this.statusMessage))
     throw new errors.Error('ERR_INVALID_CHAR', 'statusMessage');
 
   var statusLine = 'HTTP/1.1 ' + statusCode + ' ' + this.statusMessage + CRLF;