package.jsonとbabel.config.jsの下記proposalの部分をtransformに書き換え - @babel/plugin-proposal-private-methods + @babel/plugin-transform-private-methods - @babel/plugin-proposal-private-property-in-object + @babel/plugin-transform-private…

.bashrcに追記 export RUBYOPT='-W:no-deprecated'$ source ~/.bashrc