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

user_7841415 0
Viewed 98023

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?

ecmascript-6 javascript
4 Answers
user_10876230

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
user_25676830
user_43656260

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.

user_35274990
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