console.assert(value[, message][, ...])
A simple assertion test that verifies whether value is truthy. If it is not, an AssertionError is thrown. If provided, the error message is formatted using util.format() and used as the error message.
console.assert(true, 'does nothing');
// OK
console.assert(false, 'Whoops %s', 'didn\'t work');
// AssertionError: Whoops didn't work