const { IMP } = window;

import { RequestPayParams, RequestPayResponse } from 'iamport-typings';

const onClickPayment = () => {
  const { IMP } = window;
  IMP.init('your_imp_uid');

  const params: RequestPayParams = {
    ...
  };

  IMP.request_pay(params, onPaymentAccepted);
};

const onPaymentAccepted = (response: RequestPayResponse) => {
  const { imp_uid, merchant_uid } = response;
  console.log(imp_uid, merchant_uid);
};