JSFiddle - React, Tailwind, and code Playground
JavaScript
var patt = /<input.*?(\[(\d)\])(\[(\d)\]){0,1}.*/g
var res = patt.exec(' <input type="text" name="questions[0][1][question]" />');
alert('First number: ' + res[2] + "\nSecond number: " + res[4]);