it is easy to get value of selected option in ts file using (change) event binding
  <select name="months" (change)="onMonthsChange($event)"  >
  <option value="1"> January</option>
  <option value="2"> February </option>
  <option value="3"> March</option>
  <option value="4"> April</option>
  </select>import { Component, OnInit } from '@angular/core'; 
@Component({
  selector: 'app-test',
  template: `
  <h2> Welcome {{name}} </h2>
  <select name="months" (change)="onMonthsChange($event)"  >
  <option value="1"> January</option>
  <option value="2"> February</option>
  <option value="3"> March</option>
  <option value="4"> April</option>
  </select>
  `,
  styles: [`   `]
})
export class TestComponent implements OnInit {
  public name = "Amey Raut";  
  constructor() { }
  ngOnInit() {
  }
  onMonthsChange(event){ 
    console.log(event.target.value);  
    //will display value for selected Month eg. "3" 
    console.log(event.target.options[event.target.options.selectedIndex].text); 
    //will display Text for selected Month eg. "March"
  }
   
}