Answers for "onchange in html5"

js select on change value

document.getElementById('my-select').addEventListener('change', function() {
  console.log('You selected: ', this.value);
});

onchange event

<select class='select-option' [(ngModel)]="selected"
     (change)='onOptionsSelected($event)'>
   <option class='option'  *ngFor='let option of dropDownData' 
   [value]="option.seo_val">{{option.text_val}}</option>
</select>

public onOptionsSelected(event) {
   const value = event.target.value;
   this.selected = value;
   console.log(value);
}