如何更改JavaScript中的href链接？

Question

我有一个带有语言的bootstrap 4导航栏，当我选择语言时，请使用javascript更改url和按钮文本。 当我选择法语时，将所有页面网址更改为“ / fr / about”“ / fr / contact” 如何更改网址，无论何时单击导航项，如果选择了about us，请将网址更改为/fr/about，还更改下拉菜单href

//header.ejs
  <nav>
    <div class="dropdown">
 <ul class="navbar-nav mr-auto">
            <li class="nav-item dropdown mr-4">
                <a class="nav-link dropdown-toggle" href="/en/contact" id="navbarDropdownProvider" data-toggle="dropdown"
                    aria-haspopup="true" aria-expanded="false">
                   about us
                </a>
</li>
<li class="nav-item dropdown mr-4">
                <a class="nav-link dropdown-toggle" href="/en/contact" id="navbarDropdownProvider" data-toggle="dropdown"
                    aria-haspopup="true" aria-expanded="false">
                   contact us
                </a>
</li>
</ul>
      <button id="language" class="btn btn-warning dropdown-toggle" type="button" id="dropdownMenu2"
        data-toggle="dropdown" aria-haspopup="true" aria-expanded="false" onclick="clickButton()">
        English
      </button>
      <div id="languagelist" class="dropdown-menu" aria-labelledby="dropdownMenu2" onclick="clickItem(); return false">
        <a class="dropdown-item" href="/en">English</a>
        <a class="dropdown-item" href="/fr">French</a>
      </div>
    </div>
  </nav>


//index.ejs

  <%- include header.ejs %>
  <h1>Welcome to My Site</h1>

//app.js
var express = require('express');
var app = express();
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs')
var languageRouter = require('./routes/language');

app.use('/:lan', languageRouter);
app.use('/:lan/contact', contactusRouter);
app.use('/:lan/aboutus', aboutusRouter);

//language.js
var express = require('express');
var router = express.Router();
router.get('/', function (req, res) {
    res.render('index.ejs'});
});
module.exports = router;
//aboutus.js
var express = require('express');
var router = express.Router();
router.get('/', function (req, res) {
    res.render('aboutus.ejs');
});
module.exports = router;