Underscore doesn't work in Coffeescript's console

Question

I\'ve just started using Coffeescript and the Coffeescript console, and Underscore. However, whenever I define a function, Coffeescript decides that _ means tha

Answer 1

The CoffeeScript REPL has this JavaScript at its heart:

try {
  _ = global._;
  returnValue = CoffeeScript["eval"]("_=(" + code + "\n)", {
    filename: 'repl',
    modulename: 'repl'
  });
  if (returnValue === void 0) {
    global._ = _;
  }
  repl.output.write("" + (inspect(returnValue, false, 2, enableColours)) + "\n");
} catch (err) {
  error(err);
}

So if the last command returned something then _ will be that something. I can't find any documentation about this though but searching for _ isn't a terribly productive activity. If you want to use Underscore.js in the CoffeeScript REPL, you'll have to call it something other than _.

Thanks to Trevor Burnham (who wrote the book so I think we can trust him on this) we know that the CoffeeScript REPL uses _ as the last result to match the behavior of the node.js REPL:

REPL Features
[...]
The special variable _ (underscore) contains the result of the last expression.

Ruby's irb does the same thing.