hi, please check following link, this can help you:

encodedna.com/javascript/how-to-save-form-data-in…

JavaScript won't have access to write to the system, but you can generate a text file and send it to download. stackoverflow.com/a/18197341

Create txt file using JavaScript Stackoverflow

Read data from HTML form

<input type="text" name="name" id="your_id" value="value" />

let nameValue = document.getElementById("your_id").value;

May be it will help you!!