Sample Code

App.js

import React, {Component} from 'react';  
import {Platform, StyleSheet, Button, View} from 'react-native';    
import {NativeModules} from 'react-native';
import RNPgReactNativeSDK from 'react-native-pg-react-native-sdk'
import axios from 'axios';
axios.defaults.timeout = 5000;

var testUrl = "https://test.cashfree.com/api/v2/cftoken/order";
var prodUrl = "https://api.cashfree.com/api/v2/cftoken/order";

export default class App extends Component {

  _startProcess() {

    var orderId;
    const apiKey = "--appIdhere--";
    const apiSecret = "--secrethere--";
    const env = "TEST";

      orderId = "Order" + parseInt((100000000 * Math.random()));
      let orderApiMap = {
        "orderId": orderId,
        "orderAmount": "1",
        "orderCurrency": "INR"
      }
    
      const postParams = {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'x-client-id': apiKey,
          'x-client-secret': apiSecret
        },
        body: JSON.stringify(orderApiMap)
      }
    
      var cfToken;
      fetch(testUrl, postParams).then(response => {
      // console.log("data" + response.json());
      return response.json()
      })
        .then(data => {
          cfToken = data.cftoken
          console.log("Token : " + data.cftoken);
          startPayment(cfToken)
        })
  
    
    function startPayment(cfToken) {
      var map = {
        "orderId": orderId,
        "orderAmount": "1",
        "appId": apiKey,
        "tokenData": cfToken,
        "orderCurrency": "INR",
        "orderNote": "asdasdasd",
        "notifyUrl": "https://test.gocashfree.com/notify",
        "customerName": "Cashfree User",
        "verifyExpiry": "100",
        "customerPhone": "9999999999",
        "customerEmail": "cashfree@cashfree.com"
      }
      
      RNPgReactNativeSDK.startPaymentWEB(map,env,(result) => {
        console.log(result);
        var obj = JSON.parse(result, function (key, value) {
        console.log(key + "::" + value);
        // Do something with the result
        })
      });
    }

  }

  render() {
    return (
      <View style={{flex: 1, alignItems: 'center', justifyContent: 'center'}}>
                    <Button onPress={()=>this._startProcess()} title="WEB" />
      </View>

    );
  }
}