Editing an external Json file in js : got error Uncaught ReferenceError: require is not defined

Question

I'm trying to edit a json file. Here is my code:

const fs = require("fs");
const users = require("./users");
let user = {
name: "New User",
age: 30,
language: ["PHP", "Go", "JavaScript"]
};
users.push(user);
fs.writeFile("users.json", JSON.stringify(users), err => {
    if (err) throw err;

console.log("Done writing"); // Success
});

But I am getting an error as Uncaught ReferenceError: require is not defined

I am new in javascript. Can any one help me in getting this issue resolved

Note: I want to edit and save external json file through js