【JS】验证表单是否空白验证

<form action="main.html" id="loginForm" name="loginForm" onsubmit="return checkLogin()">
				<p class="logo" width="100x">XX系统管理系统</p><br>
			<input name="username" type="tel" class="Input" placeholder="用户名" value=""><br>
			<input name="passwd" type="password" class="Input" placeholder="密码" value=""><br>
			<button class="botton" id="loginbutton">登陆</button>
			</form>

function checkLogin() {

    // alert("提交表单检查")
    //检查表单是否填写了数据
    username=document.loginForm.username.value;
    passwd=document.loginForm.passwd.value;
    if(username==""||passwd==""){
        alert("用户名或密码为空！");
        return false;
    }else {
        return true
    }
}