TypeError：无法读取属性＆＃39; writeHead＆＃39;未定义的节点js

Question

您好我在节点中运行真正的vanilla服务器并且此错误不断弹出，我甚至无法跟踪它，因为在我看来，没有任何可能出错的地方？

function send404(request, response) {
        response.writeHead(404, {'Content-Type': 'text/plain'});
        response.write('Error 404: resource not found. ');
        response.end();
    };

Server.js

var server = http.createServer(function (request, response) {
        var filePath = false;

        if (request.url === '/') {
            filePath = 'public/index.html';
        } else {
            filePath = 'public' + request.url;
        }
        var absPath = './' + filePath;
        serveStatic(response, cache, absPath);
        var filePath = false;

        if (request.url === '/' ) {
            filePath = 'public/index.html';
        } else {
            filePath = 'public' + request.url;
        }

        var absPath = './' + filePath;
        serveStatic(response, cache, absPath);
    });


    server.listen(3000, function() {
        console.log('Server listening on port 3000.');
    });