Goodbye CoffeeScript, Hello TypeScript(blog.heapanalytics.com)

  class GraphQuery extends Query {
    static parse(object: any): Try<GraphQuery> {
      return TimeRange.parse(object.over).flatMap((timeRange: TimeRange) => {
        return Filter.parse(object.where).flatMap((filter: Option<Filter>) => {
          return GroupBy.parse(object.by).flatMap((groupBy: Option<GroupBy>) => {
            return new Success(new GraphQuery(
              filter,
              groupBy,
              timeRange
            ));
          });
        });
      });
    }
  }

  parse : Any -> Try GraphQuery
  parse object = do 
    timeRange <- TimeRange.parse object.over
    filter    <- Filter.parse object.where
    groupBy   <- GroupBy.parse object.by
    return (createGraphQuery filter groupBy timeRange)

    let some_func = callback => callback(new Error('boom'));

    let some_func = err => console.log(err || 'everything is fine');

    let some_func = (callback) => callback(new Error('boom'))

    let some_other_func = (err) => console.log(err || 'everything is fine')

    let some_func = co(function*() {
        try { 
            const someData = yield asyncRequest(some_url);
            console.log('asyncRequest resolved with %j', someData)
        }
        catch(e) {
            console.log('asyncRequest rejected with %j', e);
        }
    });

  * Comprehensions (more flexible with Coffeescript).  Wait, that's ES7 now.
  * Template strings
  * For .. Of loops
  * Destructing
  * Classes. ES2015 has an awful implementation of this, without allowing an syntax for binding methods.  Also enforces the somewhat arbitrary requirement of function properties only, as opposed to any type I choose.  Don't forget, mixins with Coffeescript classes is a breeze, but no support with ES2015.
  * Arrow functions.  Unnecessary syntax with ES2015 (the parens even without arguments), not to mention confusing implicit return.
  * Generators with ES2105.  If you find a use for these in front end web dev I'll buy you a beer.