MyJs v1.3
Click the add-on icon to write your own JavaScript.
You can save 10 JavaScripts (click the checkboxes 1~10 below and then click the overwrite button to save it).
Please use it in the Context Menu of the web page (which appears when you click the right mouse button).
I added a JavaScript to the menu in advance, and I am using it. Its function is to let you try to use JavaScript to full screen, you can use it or ignore it.