In Chrome: Open Chrome DevTools -> Sources panel, browse in left navigation, or press Ctrl+O to open files included in the page.
Then you can edit the file and press Ctrl+S to save the change, and see what happens with the new codes. I usually do it with the help of break points.
If you are debugging and want to save the changes to your local file system, you could right click on the navigation, and select Add folder to workspace:
In such case, if you save your changes in DevTools, the relevant file in your file system will be updated as well.
For example I add a folder to workspace, in it there is a 1.js:
Then I edit the JS file in DevTools, the change is updated in local file system immediately:
