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JavaScript KC Message Board › void 0

void 0

Jeremy D.
jdarlingkc
Kansas City, MO
Post #: 1
You learn something new every day. For so long I've been typing out (typeof(something)==='undefined')

But, today I was browsing the code to PUID (https://github.com/pi...­) and noticed a bunch of references to void 0:

{
value: options === void 0 ? defaultValue : anotherValue
}

So, of course, I had to fire up Node and see exactly what this magical void 0 was. Turns out its a undefined reference that works every time.

So, typeof(void 0) returns 'undefined', thus comparison of a variable to void 0 will tell you if it is defined or not.

Just thought I'd pass it on.
Andrew D.
adunkman
Washington, DC
Post #: 13
Yes! void 0 is preferred by the Coffeescript compiler as well to represent undefined: http://coffeescript.o...­
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