how to update by using id in express js and mongoose with parameters

<div class="header">
    <a href="./viewdatabase">Get Details in json format</a>
    <a href="./getdetails">refresh</a>
</div>
<hr>

<% if(details!=null) { %>
    <table id="bordertable">
        <tr>
            <th>Name</th>
            <th>Age</th>
            <th>Gender</th>
            <th>Locality</th>
            <% details.forEach((item)=>{ %>
        <tr>
            <td>
                <%= item.name%>`enter code here`
                <a href="/update/<%= item._id %>" >update</a>
            </td>
            <td>
                <%= item.age %>
            </td>
            <td>
                <%= item.gender%>
            </td>
            <td>
                <%= item.locality%>
            </td>

        </tr>
        <% }) %>
    </table>
    <% } %>

    app.get('/update/:id', (req, res) => {    
    var id = req.params.id; 
       res.render('edit.ejs');  
       console.log(req.params.id);
    });

    app.post('/edit',(req, res) => {
     gymApplicant.updateOne({ _id:req.params.id }, {$set: {
        age: req.body.age,
        gender:req.body.gender
     }
     }, function (err, result) {
          if (err) {
          console.log(err);
        } else {
         console.log("Post Updated successfully");
         res.render('abc.ejs');
     }
    });
    });