JSFiddle - React, Tailwind, and code Playground

HTML

<div class="workline"><input type="text" class="work1" id="w1" /></div>

CSS

.workline{
	color: red;
	position: relative;
	width: 0;
}
.workline:after {
	position: absolute;
	background: red;
	top: 15px;
	left: 5px;
	height: 1px;
	width: 100%;
	content: '';
}
.work1{
	color: black;
}

JavaScript

$(document).ready(function(){
    $('.workline input').bind('keyup', function() {
		var latWidth = 6.5;
		var varWidth = ($(this).val().length)*latWidth;
		$(this).parents('.workline').css('width', varWidth);
    });
});