问当我尝试提交HTML表单时显示错误“Cannot POST”

EN

 // Node.js JavaScript code

 const express = require ("express");
  const bodyParser = require("body-parser");

   const app = express();

    app.use(bodyParser.urlencoded({extended:true}));

 app.get("/",function(req,res){
  res.sendFile(__dirname + "/index.html");
    });


app.post('/', function (req, res) {

var num1 = Number(req.body.num1);
 var num2 = Number(req.body.num2);

  var result = num1 + num2;

  res.send("the result is"+ result);

});


 app.listen(3000,function(){
  console.log("starting");
  });