Nodejs reported an error

  node.js, question

var express, ejs, routes, app, cons;

express = require(“express”); ejs = require(‘ejs’); routes =
require(‘./routes/index’); cons = require(‘consolidate’);

app = express();

App.use (express.static (_ _ dirname plus’ /public’); app.set(‘port’,
process.env.PORT || 3000); app.set(‘views’, “./views”);
//app.engine(‘html’, require(‘ejs’).renderFile); app.set(‘view
engines’, “ejs”);

app.get(“/”, function(req, res){ //res.render(‘index’, { title:
‘Hey’, message: ‘Hello there!’ }); res.render(“index”,{“title”:”ok”});
res.end(); });

app.listen(3000,function(){

console.log(app.port); console.log(“Listening port:3000”); });

res.render(“index”,{“title”:”ok”});
Why?, please Don’t understand

Error: No default engine was specified and no extension was provided.
at new View
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/view.js:48:42)
at EventEmitter.app.render
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/application.js:545:12)
at ServerResponse.res.render
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/response.js:938:7)
at /Users/songt/songt/develop/nodejs/study/myshow/app.js:29:6 at
Layer.handle [as handle_request]
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/router/layer.js:82:5)
at next
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/router/route.js:110:13)
at Route.dispatch
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/router/route.js:91:3)
at Layer.handle [as handle_request]
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/router/layer.js:82:5)
at
/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/router/index.js:267:22
at Function.proto.process_params
(/Users/songt/songt/develop/nodejs/study/myshow/node_modules/express/lib/router/index.js:321:12)

In the new view, no default engine is specified, and no extension is provided. Understanding English is not very good either.
Error: No default engine was specified and no extension was provided.