The best replacement for coffeescript is javascript.

The best alternatives to coffeescript are rated as following:
★★★★★  javascript
★★★★  typescript
★★★  livescript
★★★  clojurescript
★★  es6
★★  coffeescriptredux
★  opal
  dart

Your alternative for coffeescript is not listed? Suggest!
Speaking about coffeescript, one probably shouldn't forget about node.

Other search terms related to coffeescript and their ratings are:
★★★★★ node
★★★★★ jquery
★★★★ angular
★★★ requirejs
★★★ rails
★★★ backbone
★ ember
★ jasmine
You have in mind a companion for coffeescript and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of coffeescript in all years. Click on graph for more.
coffeescript
javascript
typescript