关于视频播放问题？按照js高级程序设计指南上508页写的，但不知道哪错了？

Question

<div class="media">
        <div class="video">
            <video id="player" src="../1.mkv" poster="../images/poster.jpg" width="600" height="446"></video>
        </div>
        <div class="controls">
            <input type="button" value="Play" id="video-btn">
            <span id="curtime">0</span><span id="duration">0</span>
        </div>
    </div>
    <script>
        var player=document.getElementById("player");
        var btn=document.getElementById("video-btn");
        var curtime=document.getElementById("curtime");
        var duration=document.getElementById("duration");
        duration.innerHTML=player.duration;
        btn.onClick=function(event){
            if(btn.paused){
                player.play();
                btn.value="Pause";
            }else{
                player.pause();
                btn.value="Play";
            }
        };
        setInterval(function(){
            curtime.innerHTML=player.currentTime;
        },250);
    </script>

Answer 1

btn.onclick=function(event){
  if(player.paused){