nodejs socket.io chat，点击按钮累积触发器发射

Question

客户代码：

$(document).off('click.chatBtn').on('click.chatBtn','.chatBtn',function(e){
    var $target = $(e.currentTarget);
    var $charInput = $target.siblings('.charInput');
    var val = $charInput.val();
    var userName = $userName.val();
    if(!userName){
        alert('please input name');
        return;
    }
    socket = io.connect();
    socket.emit('chat',userName+"说："+val);
    socket.on('chat',function(data){
        var $it = addMsg(data);
        $it.appendTo($message);
    });
});

服务器代码：

 socket.on('chat',function(data){
    io.sockets.emit('chat',data);
});

当我点击chatBtn时，首先点击，显示一个消息，两次点击，显示两个消息，三次点击，显示三个消息...

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