Variable Scope
You need to know three rules to understand scoping in CoffeeScript:
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Every function creates its own scope.
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Functions are the only constructs that create scope.
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Each variable lives in the outermost scope in which a value is (potentially) assigned to it.
The first two rules are an innate part of the JavaScript language. (More precisely, it’s how variables are scoped with the var keyword. A different scoping keyword, let, is also supported in the ECMAScript 6 draft spec and a handful of forward-looking JavaScript runtimes.) CoffeeScript follows suit, which means that conditionals and loops do not create scope.
The last rule allows CoffeeScript to do away with var. If you write myBologna = ’Oscar Mayer’, it’s understood that you ...
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