When starting beef the following is displayed

[ 8:46:15][!] [AdminUI] Error: Could not minify JavaScript file: web_ui_all
388
[ 8:46:15] |_ [AdminUI] Ensure nodejs is installed and node' is in $PATH` !

When investing the error there is a requirement for harmony: true to be set for ES6 js.

add this to the opts hash passed to the compiler will resolve this issue

ruby opts = { :output => { :comments => :none }, :compress => { :dead_code => true, }, harmony: true }