db.js

const db = openDatabase(
  "mydb",
  "1.0",
  "Test DB",
  2 * 1024 * 1024, (...args) => {
    console.log("db created! ", args);
  });

db.transaction((tx) => {
  tx.executeSql("CREATE TABLE IF NOT EXISTS LOGS (id unique, log)");
  setTimeout(readWriteLoops, 500);
});

let i = 0;

function readWriteLoops() {
  setInterval(() => {
    db.transaction((tx) => {
      tx.executeSql(
        "INSERT INTO LOGS (id,log) VALUES (?, ?)",
        [i, `log entry #${i++}`]
      );
    });
  }, 100);
  setTimeout(() => {
    setInterval(() => {
      db.transaction((tx) => {
        tx.executeSql(
          "SELECT * FROM LOGS",
          [],
          (tx, results) => {
            const vals = Object.values(results.rows);
            const last = vals[vals.length - 1];
            console.log(last.id, last.log);
          },
          (...args) => {
            console.error("something bad happened:", args);
          });

      });
    }, 100);
  }, 50);
}