199 ServerResponse.prototype.statusCode = 200;  method in ServerResponse
250   this.writeHead(this.statusCode);
254 function writeHead(statusCode, reason, obj) {  argument
255   const originalStatusCode = statusCode;
257   statusCode |= 0;
258   if (statusCode < 100 || statusCode > 999) {
269       this.statusMessage = STATUS_CODES[statusCode] || 'unknown';
272   this.statusCode = statusCode;
309   const statusLine = `HTTP/1.1 ${statusCode} ${this.statusMessage}${CRLF}`;
311   if (statusCode === 204 || statusCode === 304 ||
312       (statusCode >= 100 && statusCode <= 199)) {
408         res.statusCode = 500;