我对一个查询感到困惑：当我从运行在不同源的前端调用 POST 请求到运行在不同源的后端时，为什么我的包含表单数据的 POST 请求没有被 CORS 策略阻止？
我的 Nodejs 代码包含以下代码行：
const express = require('express');
const app = express();
const path = require("path");
const multer = require('multer');
const upload = multer({
dest:"uploads/"
})
app.use("/image",express.static(path.join(__dirname,"uploads")))
app.post("/upload",upload.single('profile'),(req,res)=>{
console.log(req.body);
console.log(req.file);
res.send("uploaded");
})
app.listen(8080,(err)=>{
if (err) {
console.log("Opps");
}
},()=>{
console.log("listening at port 8080");
})
我的前端代码：假设我正在运行我的index.htmlhttp://127.0.0.1:5500/index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js"></script>
<title>Form with Photos</title>
</head>
<body>
<form onsubmit="handleForm(event)">
<input type="text" name="username"> <br>
<input …