JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>

JavaScript

var dt = "07/2017";

alert(moment(dt,"MM/YYYYY").format('YYMM'));

alert(moment(dt,"MM/YYYYY").add(-1, 'months').format('YYMM'));