cors js code example

Example 1: node express cors headers

var express = require('express')
var cors = require('cors')
var app = express()

app.use(cors())

app.get('/products/:id', function (req, res, next) {
  res.json({msg: 'This is CORS-enabled for all origins!'})
})

app.listen(80, function () {
  console.log('CORS-enabled web server listening on port 80')
})

Example 2: express js cors

var express = require('express')
var cors = require('cors')  //use this
var app = express()

app.use(cors()) //and this

app.get('/user/:id', function (req, res, next) {
  res.json({user: 'CORS enabled'})
})

app.listen(5000, function () {
  console.log('CORS-enabled web server listening on port 5000')
})

Example 3: cors express

var allowedOrigins = ['http://localhost:3000',
                      'http://yourapp.com'];
app.use(cors({  
  origin: function(origin, callback){
    // allow requests with no origin     
    // (like mobile apps or curl requests)    
    if(!origin) 
      return callback(null, true);    
    if(allowedOrigins.indexOf(origin) === -1){
      var msg = 'The CORS policy for this site does not ' +                
          'allow access from the specified Origin.';      
      return callback(new Error(msg), false);    
    }    
    return callback(null, true);  
  }
}));

Example 4: what is cors

“CORS” stands for Cross-Origin Resource Sharing. 
It allows you to make requests from one website to another website 
in the browser, which is normally prohibited by another browser policy 
called the Same-Origin Policy (SOP).

Example 5: cors package install npm

var express = require('express')var cors = require('cors')var app = express() app.get('/products/:id', cors(), function (req, res, next) {  res.json({msg: 'This is CORS-enabled for a Single Route'})}) app.listen(80, function () {  console.log('CORS-enabled web server listening on port 80')})

Example 6: what is CORS

Use CORS to allow cross-origin access. 
CORS is a part of HTTP that lets servers specify any other hosts 
from which a browser should permit loading of content.

How to block cross-origin access
To prevent cross-origin writes, 
	check an unguessable token in the request — known as a Cross-Site Request Forgery (CSRF) token. 
    prevent cross-origin reads of pages that require this token.
To prevent cross-origin reads of a resource, 
	ensure that it is not embeddable.
    prevent embedding because embedding a resource always leaks some information about it.
To prevent cross-origin embeds, 
	ensure that your resource cannot be interpreted
    Browsers may not respect the Content-Type header. 
For example, if you point a <script> tag at an HTML document, the browser will try to parse the HTML as JavaScript. When your resource is not an entry point to your site, you can also use a CSRF token to prevent embedding.