BTW the code does not completely replicate the ternary operator (at least how it gets evaluated in most languages).
<predicate> ? <consequent> : <alternative>
in most languages if the predicate is an expression that evaluates to true then only the <consequent> gets evaluated and the <alternative> if the <predicate> is set to false then only the <alternative> expression gets evaluated
open up your JS console and type
false ? console.log("never printed") : console.log("LOGGED!")
You’ll get LOGGED in the console, in the main function above both a and a-1 are evaluated regardless of the result of a > b.