Well you have to ask for whom. For existing coffee script developers, they can keep using it until they get up to date with ES6. It's a language and it takes time to learn.

I'm not sure I'd agree that there is the concept of a "coffeescript" developer. Coffeescript is an intermediate language in the same way SASS is to CSS.

If you program in SASS and feel out of touch touch with CSS, then I feel you've lost your way. In the same vein, if a CoffeeScript developer, needs "significant" time and investment to transition to ES6, then I would think there is a significant erosion in that developer's understanding of CoffeeScript's ES5 underpinnings.

Yeah you are right. I was making a general point in the case of coffee script perhaps it's irrelevant. I don't write it so I am not in the know.

Except sass is a fully backwards compatible superset to CSS, and coffescript is definitely not that to JavaScript.

Really? Are you sure? If CoffeeScript isn't fully compatible with JS then what is it? I mean at some point it has to go through a JS interpreter to run.

I created a coffee file called list.coffee with:

    var list = [1, 2, 3, 4, 5];

When I run `coffee list.coffee` I get:

    /home/****/Code/coffee/thing.coffee:1:1: error: reserved word 'var'
    var list = [1, 2, 3, 4, 5];
    ^^^

The coffeescript interpreter is standalone and does not turn it in to JS.