The expression 5 || 0 evaluates to 5. In JavaScript, the logical OR operator (||) returns the first truthy operand encountered, or the last operand if all are falsy. Since 5 is truthy, it is returned immediately without evaluating the second operand. This behavior is leveraged in common JavaScript patterns like default parameter values before ES6: function foo(arg) { arg = arg || defaultValue; }. It's important to note that || returns the actual operand value, not a boolean.