In most cases, en empty block represents a missing implementation:
if (something) { // Non-Compliant // What ? } if (something) { // Compliant doSomething(); } for (var i = 0; i < length; i++) { // Non-Compliant // Empty on purpose or missing piece of code ? } for (var i = 0; i < length; i++) { // Compliant doSomething(); }