JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
    <div class="block">
        block
        </div>

    <div class="content">
        content
    </div>
    
    </div>

CSS

body {
    margin: 0px;
    padding: 0px;
}
.block {
    background: blue;
    height: 300px;
    width: 100%;
    position: fixed;
}
.content {
	background: red;
	margin-top: 300px;
	top: 0;
	width: 100%;
    height: 100%;
	z-index: 100;
	position: absolute;
}
.wrapper {
    background: #ccc none repeat scroll 0 0;
    position: absolute;
    width: 100%;
    height: 100%;
    overflow: auto;
  }

JavaScript

$( ".wrapper" ).scrollTop( 300 );