Ruby,Node.js真偽値を得る方法7選

ruby

puts (!0)
# =>false
puts (!1)
# =>false
puts (!!0)
# =>true
puts (!!1)
# =>true
puts (!"")
# =>warning string literal in condition
# =>false
puts (![])
# =>false
puts (!{})
# =>false

Node.js

console.log(!0)
//=>true
console.log(!1)
//=>false
console.log(!!0)
//=>false
console.log(!!1)
//=>true
console.log(!"")
//=>true
console.log(![])
//=>false
console.log(!{})
//=>false