关于在html的form中使用JavaScript限制密码长度
请问如何在html的form里实现：限制密码长度为九位字母以内？
已经在html中插入了jquery包，但是在js中输入限制密码长度的代码没有反应，谢谢各位了～
以下是我的代码
html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Start the order</title>
<link rel="stylesheet" href="order.css">
</head>
<body>
<div id="container">
<div id="login-wrapper">
<div class="page">
<h1>Login</h1>
<form name="login-form" method="post" autocomplete="off">
<p class="success login-success"></p>
<label id="input">Username <span>Please enter your username</span></label>
<input type="text" name="username" id="input">
<p class="error username-error"></p>
<label id="input">Password <span>Please enter your password</span></label>
****<input type="password" name="password" id="input">****
<p class="error password-error"></p>
<div id="select">
<select name="select" placeholder="Please choose the size of the burger" id="select">
<option>Please choose the size of the burger</option>
<option>6oz Larger 7.00 euro</option>
<option>10oz Extra-Larger 9.00 euro</option>
<option class="pwd">16oz Supersize 17.50 euro</option>
</select>
</div>
<div>Please choose the number of the burger</div>
<input type="number"
min="1";
max="100"
step="1"
value="1" id="input">
<input type="text" name="Discount Code" placeholder="Discount Code" id="input">
<a href="menu.html">
<input type="submit" name="login-submition" value="login" id="btn">
<p class="error login-error"></p>
</a>
</div>
</div>
</div>
</div>
****<script type="text/javascript" src="jquery-3.1.1.min.js"></script>****
<script src="order.js"></script>
</form>
</body>
</html>
javascript
function showError(errorElement, errorMessage){
document.querySelector("." + errorElement).classList.add("display-error");
document.querySelector("." + errorElement).innerHTML = errorMessage;
}
function clearError(){
let errors = document.querySelectorAll(".error");
for(let error of errors){
error.classList.remove("display-error");
}
}
let form = document.forms['login-form'];
form.onsubmit = function(event){
clearError();
if(form.username.value === ""){
showError("username-error","Please check your username");
return false;
}
if(form.password.value === ""){
showError("password-error","Please check your password");
return false;
}
event.preventDefault();
}
****function pankong(){
var pwd = document.getElementsByName("pwd")[0].value;
}
if (pwd.length > 9){
alert("Password should not be more than nine charators");
}else{
var j = /^[0-9a-zA-Z]+$/;
if(j.test(pwd)){
document.tijiao.submit();
}else{
alert("Please enter in charactors");
}
}****
if(window.history.replaceState){
window.history.replaceState(null,null,window.location.href)
}
