[Some features of ECMAScript are intentionally unsupported](#unsupported). Please review both the open and closed [issues on GitHub](https://github.com/jashkenas/coffeescript/issues) to see if the feature you’re looking for has already been discussed. As a general rule, we don’t support ECMAScript syntax for features that aren’t yet finalized (at Stage 4 in the proposal approval process).
For more resources on adding to CoffeeScript, please see [the Wiki](https://github.com/jashkenas/coffeescript/wiki/%5BHowto%5D-Hacking-on-the-CoffeeScript-Compiler), especially [How The Parser Works](https://github.com/jashkenas/coffeescript/wiki/%5BHowTo%5D-How-parsing-works).
Of course, it’s entirely possible that you have a great addition, but it doesn’t fit within these constraints. Feel free to roll your own solution; you will have [plenty of company](https://github.com/jashkenas/coffeescript/wiki/In-The-Wild).