Creating a new JSON file using Javascript

Question

I have the following JSON string created by javascript which is captured from a form in HTML.

I am trying to create a new JSON file using javascript but keep getting an error in the console.

here is the script:

let business_plans = [];
const add_business_plan = (ev) => {
  ev.preventDefault(); //to stop the form submitting
  let business_plan = {
    id: Date.now(),
    businessname: document.getElementById("businessName").value,
  };
  business_plans.push(business_plan);
  document.querySelector("form").reset();
  //for display purposes only
  console.warn("added", { business_plans });
  let pre = document.querySelector("#msg pre");
  pre.textContent = "\n" + JSON.stringify(business_plans, "\t", 2);
  var dictstring = JSON.stringify(business_plan);
  var fs = require("fs");
  fs.writeFile("thing.json", dictstring, function (err, result) {
    if (err) console.log("error", err);
  });
};
document.addEventListener("DOMContentLoaded", () => {
  document
    .getElementById("btn")
    .addEventListener("click", add_business_plan);
});

here is the error in the console:

Uncaught ReferenceError: require is not defined
    at HTMLButtonElement.add_business_plan (new_json.js:25)

the error is related to this line:

  var fs = require("fs");

My question: What am I doing wrong and how do i fix this error?