A little problem with objects

Here's the question---

Check if the predicate (second argument) is truthy on all elements of a collection (first argument).

function truthCheck(collection, pre) {
  // Is everyone being true?
  return pre;
}

truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex");

Tasks---

1)truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex") should return true.

2)truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex") should return false.

3)truthCheck([{"user": "Tinky-Winky", "sex": "male", "age": 0}, {"user": "Dipsy", "sex": "male", "age": 3}, {"user": "Laa-Laa", "sex": "female", "age": 5}, {"user": "Po", "sex": "female", "age": 4}], "age") should return false.

4)truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true}, {"name": "FastFoward", "onBoat": null}], "onBoat") should return false

5)truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true, "alias": "Repete"}, {"name": "FastFoward", "onBoat": true}], "onBoat") should return true

6)truthCheck([{"single": "yes"}], "single") should return true

7)truthCheck([{"single": ""}, {"single": "double"}], "single") should return false

8)truthCheck([{"single": "double"}, {"single": undefined}], "single") should return false

9)truthCheck([{"single": "double"}, {"single": NaN}], "single") should return false

When the second argument is a string, I solved it(not a problem there)

But when the second argument is an object, I'm not sure how to solve it.(Tasks-3, 4, 7, 8, 9)

My answer

function truthCheck(collection, pre) {

  if (typeof pre === 'string') {
    for (var i=0;i<collection.length;i++) {
      if(!collection[i].hasOwnProperty(pre)) {
        return false;
      }
    }
// this part is not working
  } else if(typeof pre === 'object'){
    for(var j=0;j<collection.length;j++) {
      for(var k=0;k<collection[j].length;k++) {
        if(!collection[j][k].hasOwnProperty(pre)) {
          return false;
        }
      }
    }
  }
  return true;
}

truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex");