Access to Script at ' from origin 'null' has been blocked by CORS policy

Question

So when I am trying to import class from another javascript file, I am getting error in console like this:

Access to Script at 'file:///home/../.../JavaScript/src/index.js' from origin 'null' has been blocked by CORS policy: Invalid response. Origin 'null' is therefore not allowed access.

In my html file I am adding script file in this manner:

<script type="module" src="src/index.js"></script>

My index.js looks like this:

import Paddle from "/src/paddle";

let canvas = document.getElementById("gameScreen");
let ctx = canvas.getContext("2d");

const GAME_WIDTH = 800;
const GAME_HEIGHT = 600;

ctx.clearRect(0, 0, GAME_WIDTH, GAME_HEIGHT);
let paddle = new Paddle(GAME_WIDTH, GAME_HEIGHT);

paddle.draw(ctx);

And paddle.js:

export default class Paddle {
    constructor(gameWidth, gameHeight){
        this.width = 150;
        this.height = 30;

        this.position = {
            x: gameWidth/2 - this.width/2,
            y: gameHeight-this.height-10
        }
    }
    draw(ctx){
        ctx.fillRect(this.position.x, this.position.y, this.width, this.height); 
    }
}

I am using chromium browser. And my folder structure looks like:

/javascript
   -/src
       -index.js
       -paddle.js
   -index.html

Anyone has any idea how to avoid cors policy?

Answer 1

ES6 modules are subject to same-origin policy. You need to run your script from a local server, opening the file directly with a browser will not work.

see here ES6 module support in Chrome 62/Chrome Canary 64, does not work locally, CORS error

Answer 2

Looks like you're trying to open the web-page locally (via file:// protocol) i.e. double clicking the .html file. Unfortunately modules only work via HTTP(s), so all you need to do is use a local web server. Popular choices include:

• Live Server, a VS Code extension that adds a right-click option to run your pages with a local server.
• Node static server, a simple http server to serve static resource files from a local directory.
• Node live server is easy to install and use:

npm install -g live-server // Install globally via npm
live-server                // Run in the html's directory

Or even shorter and without altering your packages:

npx live-server

Answer 3

If you don't want to set up a local server you can actually (contrary to the previous answers) use the file:// protocol. To do so you have to run your browser with the --allow-file-access-from-files flag. Should work in all chromium based browsers such as Chrome, Opera, Brave etc.

Answer 4

file:// requests will not work, but you can run a local webserver (polymer serve, express, etc.) to use HTTP requests instead. You could even use the following Chrome extension to run a local webserver.

https://chrome.google.com/webstore/detail/web-server-for-chrome/ofhbbkphhbklhfoeikjpcbhemlocgigb?hl=en

Answer 5

Official MDN documentation mentions about running local .html files with js onboard leads to the CORS error. For more details look "JavaScript Modules" documentation page.

"Other differences between modules and standard scripts" section says:

You need to pay attention to local testing — if you try to load the HTML file locally (i.e. with a file:// URL), you'll run into CORS errors due to JavaScript module security requirements. You need to do your testing through a server.

Answer 6

To fix this error is also easy, what you need to do is to create a local web server, and then upload the Html and JS file to the webserver. Then you can browse the Html file in the web browser with the HTTP or HTTPS protocol, and then it will also load the external JS file using the HTTP or HTTPS protocol also. soloving:

1- First of all Go to the extension and download Live Server. 2- Press F1 and enter Live Server and choose Open with Live Server from menu and there you go :)

Answer 7

I faced the same issue:

Resolution:

Installed the lite-server to load the files:

• Lite-Server:BrowserSync does most of what we want in a super fast lightweight development server. It serves the static content, detects changes, refreshes the browser, and offers many customizations.

  npm i lite-server
  

include below code in package.json

"scripts": {
    "start": "lite-server"
  },

Now instead of using open / start use npm start

Answer 8

I think if you are on phone, you can use File Manager Plus, and open the HTML file with app that have an HTTP icon in right.