Javascript - objects in arrays

Javascript - objects in arrays

I'm quite a beginner in Javascript and trying to make a blackjack game.
Arrays and objects:
card = {}, //every card is an object having 3 properties: suit, number and
points
playerCards = [], //an array containing player cards (objects)
dealerCards = [], //an array containing dealer cards (objects)
I also created manually some cards for testing purposes, like this:
card = {
suit : "spade",
number : "queen",
points : 10
};
playerCards.push(card);
Then i have a function to randomly create a new card
function createCard(card, suit, number, points) {
"use strict";
var i = Math.floor(Math.random() * 4);
card.suit = suit[i];
i = Math.floor(Math.random() * 13);
card.number = number[i];
card.points = points[i];
return card;
}
It works, but when it creates a new card it replaces the last one manually
added in playerCards/dealerCards array. I can prevent it with creating a
pointless sample card and not adding it to array (then this one will be
replaced), but it doesn't seem right. So what should i do?
Thanks in advance!