无法理解我的节点JS Serveride代码中的CORS的工作
以下是我的React应用后端的Server.js代码。
我无法理解下行的工作
app.use(cors(options));
完整代码如下：
const express = require("express");
const app = express();
const cors = require("cors");
let allowed = ["http://localhost:3000", "http://localhost:4000"];
function options(req, res) {
let tmp;
let origin = req.header("Origin");
if (allowed.indexOf(origin) > -1) {
tmp = {
origin: true,
optionSuccessStatus: 200,
};
} else {
tmp = {
origin: false,
};
}
res(null, tmp);
}
app.use(cors(options));
app.listen(8000, () => {
console.log("Server running at 8000");
});
app.get("/", (req, res) => {
res.send("Hi From server hello super");
});
我的怀疑
“选项”是一个具有参数的函数。但是在行app.use（cors（options））中，如何传递参数
res（null，tmp） - ＆gt;它做了什么。它等效于res.Send（TMP）？
The below is my server.js code of my React app's backend.
I am not able to understand the working of the below line
app.use(cors(options));
The full code is as below:
const express = require("express");
const app = express();
const cors = require("cors");
let allowed = ["http://localhost:3000", "http://localhost:4000"];
function options(req, res) {
let tmp;
let origin = req.header("Origin");
if (allowed.indexOf(origin) > -1) {
tmp = {
origin: true,
optionSuccessStatus: 200,
};
} else {
tmp = {
origin: false,
};
}
res(null, tmp);
}
app.use(cors(options));
app.listen(8000, () => {
console.log("Server running at 8000");
});
app.get("/", (req, res) => {
res.send("Hi From server hello super");
});
My doubt
The "options" is a function which has arguments . But in the line app.use(cors(options)), how the arguments are passed
res(null,tmp) -> what does it do. Is it equivalent to res.send(tmp)?
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这是在使用 express-cors middleware 一些文档描述具有
options是一个函数意味着什么。具体来说，中间件调用
options函数，因为正在处理请求以确定对指定字段的影响，例如onectmethot ， 一句，您的代码具有此字段的错别字 - 它缺少s）等。optionssuccessstatus（顺便说 只是一个回调，可以让其余中间件和其他中间件继续正常执行。This is using the Express-CORS middleware which has some documentation describing what it means to have
optionsbe a function.Specifically, the
optionsfunction is called by the middleware as the request is being processed to determine the impact on the specified fields likeorigin,method,optionsSuccessStatus(by the way, your code has a typo for this field—its missing ans), etc.As the documentation shows,
resis just a callback that lets the rest of the middleware and other middlewares continue normal execution.