coffeescript - Why do we need to use unless and "?" together instead of if alone -


what need using unless , "?" when can use if in case

unless person.present?

is equivalent 

if person.present

they're not equivalent.

dosomething() unless person.present? execute if person.present null

dosomething() unless person.present execute if person.present false value

dosomething() if person.present execute if person.present true value

check compiled javascript.


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