HTML select drop-down with an input field [duplicate]
You can use input text with "list" attribute, which refers to the datalist of values.
<input type="text" name="city" list="cityname">
<datalist id="cityname">
<option value="Boston">
<option value="Cambridge">
</datalist>
This creates a free text input field that also has a drop-down to select predefined choices. Attribution for example and more information: https://www.w3.org/wiki/HTML/Elements/datalist