javascript-基础（五）

作业内容：

1. 实例演示classList对象

    let a = document.querySelector('.box')
    console.log(a.className)
    // contains(): 判断
    // remove()移除
    // replace(): 替换
    // toggle(): 动态切换class
    a.classList.contains('a1')
    a.classList.toggle('a1');
    a.classList.add('b1')
    a.classList.remove('b1')
    a.classList.replace('b1','b2')
    a.classList.toggle('b1')

2. 使用blur事件进行表单非空验证

<form action="" method="post" id="login">
      <label class="title">用户登录</label>
      <label for="email">邮箱:</label>
      <input type="email" id="email" name="email" value="" onblur="check(this)" />
      <label for="password">密码:</label>
      <input type="password" id="password" name="password"  onblur="check(this)"/>
      <button name="submit" onclick="check()">登录</button>
    </form>
    <script>
        function check(ele){
            event.preventDefault();
            event.stopPropagation()
            if(ele.id == 'email' && ele.value==0){
                alert('请检查邮箱')    
            }
            if(ele.id == 'password' && ele.value==0){
                alert('请检查密码')    
            }
        };
</script>