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

//Wrong
function truthCheck(collection, pre) {
  // Is everyone being true?
  var args = collection.prototype.slice.call(arguments);
  for(var i=0;i<args.length;i++){
    return args.indexOf(pre) !== -1 && Boolean(args[pre]);
  }
  
}

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

![Wrong](http://upload-images.jianshu.io/upload_images/316258-efda8a67f74a2ed8.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

function truthCheck(collection, pre) {
// Is everyone being true?
return collection.every(function(elements){
return elements.hasOwnProperty(pre) && Boolean(elements[pre]);
});

}

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