Mainframe ModernizationWithout Risk.

// React client — no mainframe knowledge required.
import { useState } from "react";

type InterestResponse = {
  interest: number;
  currency: "EUR" | "USD" | "SEK";
};

export function LoanCalculator() {
  const [result, setResult] = useState<InterestResponse | null>(null);

  async function calculate() {
    const res = await fetch(
      "https://api.bank.example/v1/loans/interest",
      {
        method: "POST",
        headers: {
          "Authorization": `Bearer ${token}`,
          "Content-Type":  "application/json",
        },
        body: JSON.stringify({
          principal: 250000,
          rateBps:      475,
          months:        60,
          currency:  "EUR",
        }),
      },
    );

    setResult(await res.json());
  }

  return (
    <button onClick={calculate}>
      {result ? `Interest: ${result.interest} ${result.currency}` : "Calculate"}
    </button>
  );
}