By using title attribute with change event handler, you can enable the tooltip support to selected item which is shown in input element. Whenever selection changed, need to update the title attribute value from selected item’s text content. Please refer the below code snippet,

 public onChange: any = (args: SelectEventArgs) => {
     let dropDownObj: HTMLElement = document.getElementById('ddlelement');
     dropDownObj.setAttribute('title', args.item.textContent);
  }

We can enable the tooltip option to all the list items by using title attribute with open event.Please refer the below code snippet for enable the tooltip for all the list items in open event handler.

public  onOpen: any  = (args:PopupEventArgs) => {
    // get all the list items
    let listItems: any = args.popup.element.querySelectorAll('li');
    let length: number = listItems.length;
    for (let i: number = 0; i < length; i++) {
        // set title attribute to all the list items.
        listItems[i].setAttribute('title', listItems[i].textContent);
    }
}

To install all dependent packages, use the below command

npm install

To compile and run the source files, use the below command

npm start