为啥会这样啊
以下代码为什么里面的“获取验证码”按钮点了之后倒数完不会把文字改成重新“获取验证码”，这怎么改，是不是JS出了问题？？？
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>注册</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/mdui/dist/css/mdui.min.css">
<script src="https://cdn.jsdelivr.net/npm/mdui/dist/js/mdui.min.js"></script>
</head>
<body>
<div class="mdui-container">
<form class="mdui-card mdui-shadow-2 mdui-hoverable">
<div class="mdui-card-primary">
<div class="mdui-card-primary-title">注册</div>
</div>
<div class="mdui-card-content">
<div class="mdui-textfield mdui-textfield-floating-label">
<label class="mdui-textfield-label">用户名</label>
<input class="mdui-textfield-input" type="text" required>
</div>
<div class="mdui-textfield mdui-textfield-floating-label">
<label class="mdui-textfield-label">密码</label>
<input class="mdui-textfield-input" type="password" required>
</div>
<div class="mdui-textfield mdui-textfield-floating-label">
<label class="mdui-textfield-label">确认密码</label>
<input class="mdui-textfield-input" type="password" required>
</div>
<div class="mdui-textfield mdui-textfield-floating-label">
<label class="mdui-textfield-label">图形验证码</label>
<input class="mdui-textfield-input" type="text" required>
</div>
<div class="mdui-textfield mdui-textfield-floating-label">
<label class="mdui-textfield-label">邮箱</label>
<input class="mdui-textfield-input" type="email" required>
</div>
<div class="mdui-textfield mdui-textfield-floating-label">
<label class="mdui-textfield-label">邮箱验证码</label>
<input class="mdui-textfield-input" type="text" required>
<button class="mdui-btn mdui-btn-raised mdui-ripple" id="get-verification-code">
获取验证码
</button>
</div>
</div>
<div class="mdui-card-actions">
<button class="mdui-btn mdui-btn-raised mdui-color-theme-accent">注册</button>
</div>
</form>
</div>
<script>
var btn = document.getElementById('get-verification-code');
var count = 1;
var timer = null;
btn.addEventListener('click', function() {
if (timer) {
return;
}
btn.disabled = true;
timer = setInterval(function() {
count--;
if (count <= 0) {
clearInterval(timer);
timer = null;
count = 1;
btn.disabled = false;
btn.innerHTML = "重新获取验证码";
}
btn.innerHTML = count + '秒后重新获取';
}, 1000);
});
</script>
</body>
</html>
