Which past are you talking about? Before the last years progresses, to make your javascript working on multiple browser your only choice was to lock you learning huge frameworks and toolkits like jquery and dojo, or spend hours during your weekends to get a project working on multiple platforms.
Those times were painful, now it’s much much better.
I've been writing production JavaScript since 1999. Writing compatible JS used to be a horrible pain, now everything about writing and maintaining your JS is the pain and browsers by comparison are highly forgiving.
I'm talking more ecosystem than core language changes. Though of course, core language changes are part of the build and tooling ecosystem because of everyone constantly wanting to write code that is years ahead of what browsers are actually supporting. Build and package management tooling, frameworks etc.
Those times were painful, now it’s much much better.