spfx – SharePoint Framework/ issue/ drop down change event on web part/

Here is code that should work for you:

public render(): void {
    this.domElement.innerHTML = `
      <div>
        <select id="activeDdl">
          <option value="Data1">Data1</option>
          <option value="Data1">Data2</option>
          <option value="Data1">Data3</option>
        </select>
      </div>`;

    $(document).on('change', '#activeDdl', function (e) {
      //get dropdown selected value
      var selectedVal = $("#activeDdl").find("option:selected").val();
      alert(selectedVal);
    }.bind(this));
  }

DDLSelection

Regards,
Chandani Prajapati