An additional set of data I would be interested in seeing on MDN is the original implementation date of a function, operator or other things in ECMAScript. Say that Array.prototype.flatMap was implemented in ES2019. I have use cases which I’m sure other people do too where I’m required to use an older version and sometimes don’t have access to technologies such as polyfills and down compiling. As an example recently I have been having to write scripts to be used with the Rhino 1.7.12 runtime. I’m interested to see if other people see value in this type of information being available.