basePage.ts

export default class Page{
    url: string
    constructor (url:string) {
        this.url = url
    }
    open(path: string){
        browser.url(path)
    }
}

offersPage.ts

import Page from './basePage'

class OffersPage extends Page {
    
    constructor (){
        super('/our-offers/')
    }

    open() {
        super.open(this.url)
    }

    method1 (){
      //somecode
    }
    
    method2 () {
        //somecode
    }

}

export {OffersPage}

spec.ts

import {OffersPage} from '../pages/offers'
const Offers = new OffersPage()

describe('Scenario 1', () => {
    it('should check TC#1', () => {
        Offers.open()
        //some other method calls and checks
    })
})

tsconfig.json

{
    "compilerOptions": {
        "sourceMap": true,
        "module": "commonjs",
        "target": "ES2017",
        "resolveJsonModule": true,
      "types": [
          "node",
          "@wdio/sync",
          "@wdio/mocha-framework",
          "@wdio/selenium-standalone-service"
        ]
    },
    "exclude": [
        "node_modules"
    ],
    "include": [
        "./test/**/*"
    ]

}