Shorthand for converting falsy to "false"

[huygn]

Use !! - negative's negative

var falsy1 = !!undefined // false
var falsy2 = !!null // false
var falsy3 = !!'' // false
var falsy4 = !!0 // false
var falsy5 = !!NaN // false

Javascript "falsy" values: http://stackoverflow.com/a/19839953/4328963