JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" onkeyup="search(this.value)" >

<select id="cl_sel_l"  multiple="multiple">
   <option value='2' id='c_2'>aa</option>
   <option value='3' id='c_3'>bb</option>
   <option value='4' id='c_4'>cc</option>
   <option value='5' id='c_5'>dd</option>
</select>

JavaScript

var clients = new Array();
clients[2] ='aa';
clients[3] ='bb';
clients[4] ='cc';
clients[5] ='dd';
var restore;

function search(val) {
    $('#cl_sel_l').html(restore);
    for ( var i in clients) {
        if (clients[i].toLowerCase().search(val.toLowerCase()) == -1) {
            $("#c_" + i).remove();
        }
    }
}

$(function() { restore = $('#cl_sel_l').html(); });