everythingBeTrue.js

// Everything Be True
// Check if the predicate (second argument) is truthy on all elements of a
// collection (first argument).
//
// Remember, you can access object properties through either dot notation or [] notation.

// First passing attempt:
function truthCheck(collection, pre) {
  for (let obj of collection) {
    if (!obj[pre]) return false;
  }
  return true;
}

// Second attempt using "every" method, hinted from fcc forum
function truthCheck(collection, pre) {
  return collection.every(obj => obj[pre]);
}

// Tests:
// truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy", "sex": "male"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex") should return true.
// truthCheck([{"user": "Tinky-Winky", "sex": "male"}, {"user": "Dipsy"}, {"user": "Laa-Laa", "sex": "female"}, {"user": "Po", "sex": "female"}], "sex") should return false.
// 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.
// truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true}, {"name": "FastFoward", "onBoat": null}], "onBoat") should return false
// truthCheck([{"name": "Pete", "onBoat": true}, {"name": "Repeat", "onBoat": true, "alias": "Repete"}, {"name": "FastFoward", "onBoat": true}], "onBoat") should return true
// truthCheck([{"single": "yes"}], "single") should return true
// truthCheck([{"single": ""}, {"single": "double"}], "single") should return false
// truthCheck([{"single": "double"}, {"single": undefined}], "single") should return false
// truthCheck([{"single": "double"}, {"single": NaN}], "single") should return false