JSFiddle - React, Tailwind, and code Playground

HTML

<input type='text' id='txtList' />
<ul id="fromList">
    <li class="header">ABC</li>
    <li class="item">123</li>
    <li class="item">258</li>
    <li class="item">189</li>
    <li class="item">545</li>
    <li class="header">CDE</li>
    <li class="item">789</li>
    <li class="item">215</li>
    <li class="item">897</li>
    <li class="item">999</li>
    <li class="header">E</li>
    <li class="item">701</li>
    <li class="item">566</li>
    <li class="item">511</li>
</ul>

JavaScript

$('#txtList').on('keyup', function () {
    var value = this.value;
    $('#fromList li').hide().each(function () {
        if ($(this).text().search(value) > -1) {
            $(this).prevAll('.header').first().add(this).show();
        }
    });
});