JSFiddle - React, Tailwind, and code Playground

HTML

<select class="input_panel" id="Acntname" >
<option value="0">Select</option>
<option value="1">Equity Share Capital</option>
<option value="2">Deprication Fund</option>
</select>
<input type="text" class="input_panel" id="accountname" onkeyup="showState(this.value)" />

JavaScript

window.showState = function (str) {
    var dropdown = document.getElementById('Acntname');
    var event;
    event = document.createEvent('MouseEvents');
    event.initMouseEvent('mousedown', true, true, window);
    dropdown.dispatchEvent(event);
}