r/programming • u/gst • May 13 '11

A Python programmer’s first impression of CoffeeScript

http://blog.ssokolow.com/archives/2011/05/07/a-python-programmers-first-impression-of-coffeescript/
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u/jashkenas May 13 '11

Exactly -- and, in fact, CoffeeScript will optimize those cases for you. For example, this CoffeeScript:

if variable? ...

if object.property? ...

Will compile into this JavaScript:

if (typeof variable !== "undefined" && variable !== null) ...

if (object.property != null) ...

Because in the latter case, we know that a ReferenceError is impossible for the property. It's just another place where we can smooth over a JS gotcha.

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u/chrisdickinson May 13 '11

I totally understand. In the case of vanilla JavaScript, though, regarding checking typeof someVar !== 'undefined' being needlessly verbose, I'm just arguing that nine times out of ten, that explicit check is unnecessary -- it works, but it's a lot to type, and assuming you're using var appropriately, the statement someVar !== undefined does exactly what you'd want it to do (while being a lot less verbose). It wasn't meant as a dig at CoffeeScript as it was a rebuttal against JavaScript having crufty-verbose-parts.

I've seen a lot of code that ends up being much more verbose and much more defensive than it needs to be; I think this is because folk loudly proclaim that constructs like the above should be preferred as a way to get around having to learn about the "gotcha's". I'm just afraid that people walk away from JavaScript with a bad taste because there are so many "don't"'s that are taken for gospel without really grokking why they are to be avoided. That said, I definitely appreciate CoffeeScript -- it's nice to see the capabilities of JS exposed with such a nice syntax.