CoffeeScript未定义 [英] CoffeeScript Undefined

问题描述

在javascript中检查是否从未创建过变量，我们只需执行

In javascript to check if a variable was never created, we just do

if (typeof MyVariable !== "undefined"){ ... }

我想知道我在coffeescript尝试类似

I was wonder how I do that in coffeescript?... I try something like

if (MyVariable?false){ ... }

但是这会检查如果 MyVariable 是一个函数，如果这样，将调用MyVariable将会调用void（0）或类似的东西。

but this check if MyVariable is a function if so that will call MyVariable(false) if not that will call void(0) or something like that.

推荐答案

Finally I found this easy way to do it:

if (MyVariable?){ ... }

会产生：

if (typeof MyVariable !== "undefined" && MyVariable !== null){ ... }

UPDATE 04/07/2014
演示链接

这篇关于CoffeeScript未定义的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！