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我在nodejs中創建了本地REST API服務器，它從本地Mongodb數據庫獲取數據。我還創建了一個基本網頁，它從本地請求服務器的數據。現在，當我嘗試從網頁中獲取數據，它給了我以下錯誤：無法在本地Nodejs服務器中允許跨域請求
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:4000/todos. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing).
我搜索關於計算器，發現THIS和THIS解決方案。我在我的主app.js文件中添加了建議的標題。但它仍然給出了同樣的錯誤。
以下是我的服務器app.js文件，我添加了這些標頭。
var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var routes = require('./routes/index');
var users = require('./routes/users');
var todos = require('./routes/todos');
// load mongoose package
var mongoose = require('mongoose');
// Use native Node promises
mongoose.Promise = global.Promise;
// connect to MongoDB
mongoose.connect('mongodb://localhost/todo-api')
.then(() => console.log('connection succesful'))
.catch((err) => console.error(err));
var app = express();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', routes);
app.use('/users', users);
app.use('/todos', todos);
// Add headers
app.use(function (req, res, next) {
// Website you wish to allow to connect
res.setHeader('Access-Control-Allow-Origin', '*');
// Request methods you wish to allow
res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');
// Request headers you wish to allow
res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');
// Set to true if you need the website to include cookies in the requests sent
// to the API (e.g. in case you use sessions)
res.setHeader('Access-Control-Allow-Credentials', true);
// Pass to next layer of middleware
next();
});
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
module.exports = app;
以下是網頁的代碼（Angularjs），我想從我的API中獲取數據。
dbConnection.html
<html ng-app="demo">
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.4/angular.min.js"> </script>
<head>
<title> dbConnection Demo</title>
</head>
<body ng-controller="db">
<div ng-repeat="product in db.products">
{{product._id}} </br>
</div>
</body>
<script>
var app = angular.module('demo', []);
app.controller('db', ['$http', function($http){
var store = this;
store.products = [];
$http({
method: 'GET',
url: 'http://localhost:4000/todos'
}).then(function (success){
store.products = success;
},function (error){
});
}]);
</script>
</html>
即使我已經添加標題作爲答案的建議，我得到了同樣的錯誤。我在這裏錯過了什麼？我在這個領域是完全新手。謝謝！
嘗試[CORS中間件]（https://github.com/expressjs/cors） –
沒關係，但在哪裏使用它？ – Kaushal28
鏈接中的[documentation]（https://github.com/expressjs/cors#usage）對此進行了徹底的解釋。 –