truthCheckCollection Checks if the predicate function is truthy for all elements of a collection. Use Array.prototype.every() to check if each passed object has the specified property and if it returns a truthy value. const truthCheckCollection = (collection, pre) => collection.every(obj => obj[pre]); truthCheckCollection( [ { user: 'Tinky-Winky', sex: 'male' }, { user: 'Dipsy', sex: 'male' }, ], 'sex' ); // true