JSFiddle - React, Tailwind, and code Playground

HTML

<div id="progressBar"  class="preloader__progress"></div>

CSS

* {
	-webkit-box-sizing: border-box;
	-moz-box-sizing: border-box;
	box-sizing: border-box;
}

*:before, *:after {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

body {
  background-color: #000;
}

.preloader__progress {
  position: relative;
  overflow: hidden;
  height: 40px;
  width: 996px;
  max-width: 90%;
  margin: auto;
  padding: 0;
  border: 2px solid #fff;
  background: rgb(255,255,255);
  background: -webkit-linear-gradient(left, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 41%, rgba(242,242,244,0) 41%, rgba(2,0,36,0) 100%);
  background: -moz-linear-gradient(left, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 41%, rgba(242,242,244,0) 41%, rgba(2,0,36,0) 100%);
  background: -o-linear-gradient(left, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 41%, rgba(242,242,244,0) 41%, rgba(2,0,36,0) 100%);
  background: linear-gradient(to right, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 41%, rgba(242,242,244,0) 41%, rgba(2,0,36,0) 100%);
}