JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

JavaScript

function sum(...input) {
  return _.chain(input)
          .flattenDeep()
          .reduce((i, n) => i + n)
          .value();
}
var x = [1, [2, 3, [4], [[[5]]], 6, [[7, 8]]], 9];

console.log(sum(x)); // 45