How can I create & save a new table row with custom data from a form (no jquery)

For around two weeks now I’ve been trying to get this simple add table row thing to work but i can’t seem to find any good tutorials on youtube related to what I’m asking for & most of the things I found here on stack overflow rely on jquery which i something i want to avoid using. Basically what I want my function to do is to take what the user entered in the form and put that into the cells of the new table row, then, I want to save this data to a JSON file that can then be parsed so that this data isn’t lost upon refresh.
Can someone please help me make this work

I am using an app-building software called electron however, I doubt that would have much effect on my code.

I’ve tried some basic code i found on youtube but those did absolutely nothing & anything else i could find was using jquery.
I then just looked up tutorials on google/stack overflow and incorporated the little relevant information into my addTableRow(); function but this doesnt work as I would expect – it adds a new table row with cells but the row almost immediately disappears & the cells, instead of showing what i put into the form, the only showed [objectHTMLInputElement]

My current java script code (renderer.js):

const addTableRow = () => {
  
  const name = document.getElementById("name");
  const pnum = document.getElementById("pnum");
  const age = document.getElementById("age");
  
  let table = document.getElementById("clientTable");
  
  let row = table.insertRow(-1);

  let c1 = row.insertCell(0);
  let c2 = row.insertCell(1);
  let c3 = row.insertCell(2);
  
   c1.innerHTML = `${name}`;
   c2.innerHTML = `${pnum}`;
   c3.innerHTML = `${age}`;

 table.appendChild(row);

 const clientTable = {
  row: {
    c1: c1,
    c2: c2,
    c3: c3
  }
}
fs.appendFile('table-data.json',  JSON.stringify(clientTable));
}

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The associated html (index.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">
    <link rel="stylesheet" href="app.css">
    <link rel="stylesheet">
    <title>Ezek's jsapp</title>
</head>

<body>

    <div class="tabs-container">
        <div class="tabs">
            <div class="tab active">Clients</div>
            <div class="tab">Files</div>
            <div class="tab">Settings</div>
        </div>

        <div class="content-container">
            <div class="content active">
                <h3>Clients</h3>
                <p>This is the clients tab</p>
                <form id="clForm">
                    <label for="name">Name</label><br>
                    <input type="text" id="name" name="name"><br>
                    <label for="pnum">Phone Number</label><br>
                    <input type="text" id="pnum" name="pnum"><br>
                    <label for="age">Age</label><br>
                    <input type="text" id="age" name="age"><br>
                    <button id="clBtn" onclick="addTableRow();">Submit</button>
                </form>
                <section class="wrapper-main">
                    <table id="clientTable">
                        <thead>
                            <tr>
                                <th>Name</th>
                                <th>PhoneNumber</th>
                                <th>Age</th>
                            </tr>
                        </thead>
                        <tbody>
                            <tr>
                                <td>ClientName</td>
                                <td>PhoneNumber</td>
                                <td>ClientAge</td>
                            </tr>
                            <tr>
                                <td>ClientName</td>
                                <td>PhoneNumber</td>
                                <td>ClientAge</td>
                            </tr>
                        </tbody>
                    </table>
                </section>
            </div>
            <div class="content">
                <h3>Files</h3>
                <p>This is the files tab, upload files here!</p>
            </div>
            <div class="content">
                <h3>Settings</h3>
                <p>This is the settings tab</p>
            </div>
        </div>
    </divnp>

    <script src="renderer.js"></script>

</body>

</html>