The code will output 'default'. The logical OR (||) operator returns the first truthy operand it encounters, or the last operand if all are falsy. Since NaN is falsy, the expression NaN || 'default' evaluates to 'default'. This pattern is commonly used for setting default values in JavaScript when a computation might result in NaN. However, with the introduction of the nullish coalescing operator (??) in newer JavaScript versions, there's now a more precise way to provide defaults only for null or undefined values, without affecting other falsy values like NaN, 0, or empty strings.