Automatically close all the other tags after opening a specific tag

Answer 1

Yet another answer for those who don't want to use obsolete jQuery and those who loves functional javascript

[...document.getElementsByTagName("details")].forEach( (D,_,A) =>
  D.addEventListener("toggle", E =>
    D.open && A.forEach(d =>
      d!=E.target && (d.open=false)
    )
  )
)

  
1
Demo 1



  
2
Demo 2



  
3
Demo 3