Magic code to kill various websites - you can modify and copy the page content at will_javascript skills

Everything on the page can be modified, just like editing in Word. Websites that do not allow copying can be killed by this trick. In the future, who will foolishly analyze the page code, then modify, save, refresh, and then copy it?

Code content:
javascript:document.body.contentEditable='true'; document.designMode='on';