customModal.js

import React from 'react';
import BeforeUnloadComponent from 'react-beforeunload-component';
import MyModal from 'path/MyModal';
// React Hook
const Example = () => {
    
    return (
      <div>
        <BeforeUnloadComponent
            blockRoute={true}   
            modalComponentHandler={({handleModalLeave, handleModalCancel})=>{
                return (
                    <MyModal
                        onClose={handleModalCancel}
                        onSubmit={handleModalLeave}
                    />
                )
            }}
        />  
            <form id="myform"> ... </form>
        <BeforeUnloadComponent/>
      </div>
    );
 
}
....