作成しているクイズの国名をランダムに生成する機能がありますが、同じ名前を複数回表示したくありません。どうすればそれができますか?これが私が使用しているコードです。
<div style="float:left">
<h1> <span id="questionnum"></span>. Can you locate <span id="countryquestion"></span> on the map?</h1>
</div>
<script type="text/javascript">
generateCountry();
function generateCountry(){
filenames = [ "Albania", "Andorra", "Armenia", "Austria", "Azerbaijan", "Belarus", "Belgium", "Bosnia and Herzegovina", "Bulgaria", "Croatia", "Cyprus", "Czech Republic", "Denmark", "Estonia", "Finland", "France", "Georgia", "Germany", "Greece", "Hungary", "Iceland", "Ireland", "Italy", "Latvia", "Liechtenstein", "Lithuania", "Luxembourg", "Macedonia", "Malta", "Moldova", "Monaco", "Montenegro", "The Netherlands", "Norway", "Poland", "Portugal", "Romania", "Russia", "San Marino", "Serbia", "Slovakia", "Slovenia", "Spain", "Sweden", "Switzerland", "Ukraine", "United Kingdom" ];
filename = filenames[Math.floor(Math.random()*filenames.length)];
document.getElementById('countryquestion').textContent = filename;
}
</script>