Constantly facing CORS problem accessing file with javascript

Did you follow the steps with using Node.JS from the documentation? Or do you mean that you're using 'file:///' in your browser to point directly at an HTML file on the local filesystem?
https://docs.microsoft.com/en-us/office/dev/add-ins/onenote/onenote-add-ins-getting-started

The short answer is that yes you need to host your add-in on node.js (or another webserver, but node.js is really easy to use), but you don't need to "convert" your computer into a web server as-such, since node.js can just be run from the command-line to use as a development tool (by typing "npm start", so you don't need to worry about having it running as a service, it'll just open a console window while it's running like any other console app.

There's a short explanation of what's happening when you try to run a web app from the local file system here: https://stackoverflow.com/questions/48362093/cors-request-blocked-in-locally-opened-html

If you can load your add-in from the node.js hosted webserver (e.g. https://localhost:3000/ ) then you should be able to get past this because unlike the filesystem, node.js will be able to handle the 'origin' HTTP request sent by the browser.


And yes, you can disable all of your browser's security if you absolutely must, but that wouldn't help you when you're trying to load the add-in into OneNote itself. -- e.g. disabling Chrome security: https://stackoverflow.com/questions/4819060/allow-google-chrome-to-use-xmlhttprequest-to-load-a-url-from-a-local-file
I really strongly recommend not doing this though - this is a bit of a 'nuclear' option - browser security is there to protect you against all kinds of stuff, and whatever you do with browser security disabled may not actually work when you finally do need to host it on a proper web server anyway, so there's probably not much point.

the latter, i dont know how to use nodeJs .... yet . I just abduct the file using file:\\\

Don't worry if you don't know how to use it right now, since that microsoft site tells you exactly which commands to run anyway. It seemed to work for me - I just tried this and it only took a few minutes:

1. download and install node.js - the LTS version will be fine
2. run cmd.exe (command prompt)
3. enter the command npm install -g yo generator-office -- that's going to install the office add-in generator into node.js so that you can generate the boilerplate project files for a new app/add-in (You don't need to get anything from the yeoman website, those links are just for reference/documentation)
4. enter the command yo office and follow the menu options it describes on the page to create the add-in -- that will create the actual add-in folder containing stuff like the API and all the boilerplate like index.html, with the javascript files inside a 'src' folder.
5. if you called the add-in "My Office Add-in" then type cd "My Office Add-in" (that's where index.html will be as well as package.json and loads of other files/folders)
6. type npm start in the "My Office Add-in" folder to start the web service
7. Use the browser to Navigate to https://localhost:3000/ and tell the browser to ignore the lack of a certificate -- make sure you use https:// and not http:// because the add-in configuration is configured to use SSL rather than plain HTTP

That's pretty much it. I went as far as loading it in Chrome to make sure that worked although I didn't go as far as swapping out the example code or trying the final steps with OneNote, but the node.js stuff all worked fine anyway.

So does that mean that nodeJS can help me access files on a local machine with javascript without having restriction issues?