Steps to Integrate

var responseCallBack = function (response) {
  // payment successful
  if ("generateHash" in response) {
    generateHash(response);
  } else if ("onPaymentSuccess" in response) {
    onPaymentSuccess(response);
  } else if ("onPaymentFailure" in response) {
    onPaymentFailure(response);
  } else if ("onPaymentCancel" in response) {
    onPaymentCancel(response);
  } else if ("onError" in response) {
    onError(response);
  }
};
//Handle Callback methods from SDK
function generateHash(response) {
  // Pass response param to your backend server
  // Backend will generate the hash which you need to pass to SDK
  // hashResponse: is the response which you get from your server
  var merchantSalt = `<Salt>`; //Keep Salt in the backend only.
  var resultValue = response.generateHash;
  var hashString = resultValue.hashString;
  var hashName = resultValue.hashName;
  var hash = {};
  hash[hashName] = sha512(hashString + merchantSalt);
  //Convert the hash data using sh512 and pass it to SDK.
  cordova.plugins.PayUCheckoutProCordova.hashGenerated(hash);
}

function onPaymentSuccess(response) {
  //Handle on Payment Success Response
}
function onPaymentFailure(response) {
  //Handle on Payment Failure Response
}

function onPaymentCancel(response) {
  //Handle on Payment Cancel Response
}

function onError(response) {
  //Handle on Error Response
}

var payUPaymentParams = {
  key: `<key>`,
  transactionId: `<transaction id should be less than 25 character>`,
  amount: "1.0",
  productInfo: `<string>`,
  firstName: `<string>`,
  email: `<customer email>`,
  phone: `<customer phone>`,
  ios_surl: `<ios_surl>`,
  ios_furl: `<ios_furl>`,
  android_surl: `<android_surl>`,
  android_furl: `<android_furl>`,
  environment: `<environment>`, //"0" = Prooduction,  "1" = Staging
  userCredential: `<userCredential>`, //Optional
  additionalParam: `<additionalParam>`, //Optional
  enableNativeOTP: `<boolean>`, //true:false, //Optional
  userToken: "", //Optional
  payUSIParams: `<Standing Instructions>`, //Optional
  splitPaymentDetails: `<Split Payment>`, //Optional
};

var additionalParam = {
  udf1: "user defined value 1",
  udf2: "user defined value 2",
  udf3: "user defined value 3",
  udf4: "user defined value 4",
  udf5: "user defined value 5",
  merchantAccessKey: "", //This is for lookup API, optional
  sourceId: "", //Sodexo source ID, optional
};

var spitPaymentDetails = [
  {
    type: "absolute",
    splitInfo: {
      imAJ7I: {
        aggregatorSubTxnId: "Testchild123",
        aggregatorSubAmt: "5",
      },
      qOoYIv: {
        aggregatorSubTxnId: "Testchild098",
        aggregatorSubAmt: "5",
      },
    },
  },
];

var siParamObject = {
  isFreeTrial: `<bool>`,
  billingAmount: `<number>`, //Required
  billingInterval: `<number>`, //Required
  paymentStartDate: "yyyy-dd-mm", //Required
  paymentEndDate: "yyyy-dd-mm", //Required
  billingCycle: "once", //Required //Can be any of 'daily','weekly','yearly','adhoc','once','monthly'
  remarks: "Test SI transcaction",
  billingCurrency: "INR",
  billingLimit: "ON", //ON, BEFORE, AFTER
  billingRule: "MAX", //MAX, EXACT
};

var responseCallBack = function (response) {
  if ("generateHash" in response) {
    generateHash(response);
  }
  "generateHash";
  ...................
};

function generateHash(response) {
  var merchantSalt = `<salt>`; //keep this in the backend.
  var resultValue = response.generateHash;
  var hashStringWithoutSalt = resultValue.hashString;
  var hashName = resultValue.hashName;
  var hashType = resultValue.hashType;
  var postSalt = response[resultValue.postSalt];
  var hash = `<Get Hash Backend with < hashStringWithoutSalt, hashType , postSalt >`;
  //Convert the hash data using sh512.
  //Call Call hashGenerated with HashResponse< hashName, Hash> to pass the hash from server to SDK.
  cordova.plugins.PayUCheckoutProCordova.hashGenerated(hash);
}

let payuParams = {
  payUPaymentParams: `<PayUPaymentParams>`,
  payUCheckoutProConfig: `<PayUCheckoutProConfig>`,
};
cordova.plugins.PayUCheckoutProCordova.openCheckoutScreen(
  callbackResponse,
  payuParams
);

<uses-permission android:name="android.permission.RECEIVE_SMS" />

<key>LSApplicationQueriesSchemes</key>
<array>
  <string>phonepe</string>
  <string>paytm</string>
  <string>tez</string>
</array>

<key>NSCameraUsageDescription</key>
<string>Please mention the description to give user info</string>