How to Make SVG Full Screen in Browser

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>

<svg version="1.1" id="SVG" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px"
    y="0px" width=100% height=100%>

<rect x='200' y='20' width='50' height='50' fill="black"></rect>