Why "before" and "after" attributes are discarded?

[varmiral]

https://sfc.vuejs.org/#eNp9jjtuwzAQRK9CbG2RQFwEEBjD6XKIbWRrnSgRycVypRSG7h4qNvyHy/lg3uzhndmOA0ENPm+lYzWZdOAVRozeHayDUArcN0pFGePbbjQb2iWhN4Sx6RFWH9T3ybuSnCvNTkkeN7w7LcICusBJtAoN2++cYvmzn0fwGGSE2vw7s1cOzxrhS5Vz7dwQ+efTblNw65I5GaJ2gao2hfXSvtjla2FmvfQt5VBtJP1mkkJEWFyMu2KOJJVQbElInsJuulfAm+wOOjMnjBNMf5cCiDI=

[Justineo]

before and after are now available on Element.prototype so Vue will try to set the corresponding property instead of setAttribute. You can now work around this by using ^before and ^after to force setAttribute. To prevent potential conflicts with DOM API, you should use attributes like data-before or data-after.