Answers for "laravel join with or condition"

How to add a additional condition in a join using query builder laravel 5.3?

->leftJoin('table3 AS c', function($join){
        $join->on('a.field2', '=', 'c.field2')
        ->where('a.field2', '=', true)
        ->where('a.field3', '=', 'c.field3');
})

laravel outer join

->join('answers as answers', 'responses.answer_id', '=', 'answers.id', 'left outer')