Truthy & Falsy Values

const isActive = !!user.active; is not a valid use of short-circuit evaluation. While it's a valid JavaScript expression that converts user.active to a boolean, it doesn't leverage short-circuit behavior. The double negation (!!) always evaluates both negations. True short-circuit evaluation occurs with the && and || operators, where the second operand might not be evaluated based on the first operand's value. The other options all demonstrate valid short-circuit patterns: returning a cached value or fetching if not available, safely accessing a nested property without errors, and only throwing an error if a value is nullish. These patterns are common idioms in JavaScript for writing concise, error-resistant code.