refactor: consolidate workaround logic in a function

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---

Author: kgryte

lib/node_modules/@stdlib/net/disposable-http-server/lib/main.js

@@ -29,9 +29,10 @@ var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
 var isFunction = require( '@stdlib/assert/is-function' );
 var openURL = require( '@stdlib/utils/open-url' );
 var noop = require( '@stdlib/utils/noop' );
-var Buffer = require( '@stdlib/buffer/ctor' );
+var buffer2bytelength = require( '@stdlib/buffer/ctor' ).byteLength;
 var string2buffer = require( '@stdlib/buffer/from-string' );
 var nextTick = require( '@stdlib/utils/next-tick' );
+var NODE_VERSION = require( '@stdlib/process/node-version' );
 var format = require( '@stdlib/string/format' );
 var validate = require( './validate.js' );
 var serverOpts = require( './opts.js' );
@@ -41,6 +42,7 @@ var createStore = require( './connections_store.js' );
 // VARIABLES //
 
 var debug = logger( 'disposable-http-server' );
+var SUPPORTS_BUFFER = ( parseInt( NODE_VERSION.split( '.' )[ 0 ], 10 ) < 6 );
 
 
 // FUNCTIONS //
@@ -80,6 +82,21 @@ function onClose() {
 	debug( 'Server closed.' );
 }
 
+/**
+* Returns the byte length of an encoded string.
+*
+* @private
+* @param {(string|Buffer)} str - input string
+* @returns {NonNegativeInteger} byte length
+*/
+function byteLength( str ) { // TODO: consider making a robust utility in `@stdlib/buffer/byte-length`
+	if ( SUPPORTS_BUFFER ) {
+		return buffer2bytelength( str );
+	}
+	// Earlier versions of Node.js do not support Buffers, ArrayBuffers, TypedArrays, DataViews, or SharedArrayBuffers, so we need to explicitly call `#.toString()`...
+	return buffer2bytelength( str.toString() );
+}
+
 
 // MAIN //
 
@@ -270,9 +287,7 @@ function httpServer( options ) {
 		debug( 'Sending HTML...' );
 		response.statusCode = 200;
 		response.setHeader( 'Content-Type', 'text/html' );
-
-		// TODO: we have to convert to a `string` because Node v0.10 requires a `string`. Subsequent versions support providing a `Buffer` object. Ideally, we would sniff `Buffer` support and only convert to a `string` if necessary.
-		response.setHeader( 'Content-Length', Buffer.byteLength( opts.html.toString() ) );
+		response.setHeader( 'Content-Length', byteLength( opts.html ) );
 		response.end( opts.html );
 	}
 
@@ -287,9 +302,7 @@ function httpServer( options ) {
 		debug( 'Sending JavaScript...' );
 		response.statusCode = 200;
 		response.setHeader( 'Content-Type', 'text/javascript' );
-
-		// TODO: we have to convert to a `string` because Node v0.10 requires a `string`. Subsequent versions support providing a `Buffer` object. Ideally, we would sniff `Buffer` support and only convert to a `string` if necessary.
-		response.setHeader( 'Content-Length', Buffer.byteLength( opts.javascript.toString() ) );
+		response.setHeader( 'Content-Length', byteLength( opts.javascript ) );
 		response.end( opts.javascript );
 	}