How do I define global variables in CoffeeScript?

Question

On Coffeescript.org:

bawbag = (x, y) ->
    z = (x * y)

bawbag(5, 10) 

would compile to:

var bawbag;
bawbag = function(         


        

Answer 1

Ivo nailed it, but I'll mention that there is one dirty trick you can use, though I don't recommend it if you're going for style points: You can embed JavaScript code directly in your CoffeeScript by escaping it with backticks.

However, here's why this is usually a bad idea: The CoffeeScript compiler is unaware of those variables, which means they won't obey normal CoffeeScript scoping rules. So,

`foo = 'bar'`
foo = 'something else'

compiles to

foo = 'bar';
var foo = 'something else';

and now you've got yourself two foos in different scopes. There's no way to modify the global foo from CoffeeScript code without referencing the global object, as Ivy described.

Of course, this is only a problem if you make an assignment to foo in CoffeeScript—if foo became read-only after being given its initial value (i.e. it's a global constant), then the embedded JavaScript solution approach might be kinda sorta acceptable (though still not recommended).