浏览器访问路径不提示下载而显示新页面应该如何解决

var http = require('http');var fs = require('fs');var url = require('url');var routes = {//<====路由
    "/video"(request, response) {
        fs.readFile("frag_bunny.mp4", 'binary', function (err, data) {            if (err) {                console.log(err);
                response.writeHead(500, { 'Content-Type': 'text/html' });
            } else {
                response.writeHead(200, { 'Content-Type': 'video/mp4' });//<====mp4标识
                response.write(data, 'binary');
            }
            response.end();
        });
    },    "/frag_bunny.mp4"(request, response) {
        fs.readFile("frag_bunny.mp4", 'binary', function (err, data) {            if (err) {                console.log(err);
                response.writeHead(500, { 'Content-Type': 'text/html' });
            } else {
                response.writeHead(200, { 'Content-Type': 'application/octet-stream' });//<====文件流标识
                response.write(data, 'binary');
            }
            response.end();
        });
    },    "/"(request, response) {
        response.writeHead(200, { 'Content-Type': 'text/html' }); 
        response.write(`
            <a target= "_blank" href="/video">打开页面显示播放界面</a>
            <br />
            <a target= "_blank" href="/frag_bunny.mp4">打开页面提示下载</a>
        `);
        response.end();
    },    "/404"(request, response) {
        response.writeHead(404, { 'Content-Type': 'text/html' });
        response.write("404");
        response.end();
    }
}// 创建服务器http.createServer(function (request, response) {    // 解析请求，包括文件名
    var pathname = url.parse(request.url).pathname;    // 输出请求的文件名
    console.log("Request for " + pathname + " received.");
    route = routes[pathname] 
    if (route) {
        route(request, response);
    } else {
        routes["/404"](request, response);
    }
}).listen(8889);