Parentheses group conditions:
// Is this person eligible?
let isEligible = (age >= 18 && isCitizen) || hasSpecialPermit
// Can access this resource?
let canAccess = isAdmin || (isUser && hasPermission)
Without parentheses, && has higher precedence than ||. Be explicit with parentheses to show your intent clearly:
// Ambiguous
a || b && c
// Clear
a || (b && c)
(a || b) && c