JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/tabulator/4.9.3/js/tabulator.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/tabulator/4.9.3/css/bootstrap/tabulator_bootstrap4.min.css">
<div id="example-table"></div>

CSS

.tabulator {
  font-family: -apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif,Apple Color Emoji,Segoe UI Emoji;
  font-size: 0.875em;
}

JavaScript

var updateSum = (cell) => {
  var data = cell.getData();
  var sum = Number(data.a) + Number(data.b)
  var row = cell.getRow();
  row.update({
    "ab": sum
  });
}

var table = new Tabulator("#example-table", {
  height: '100%',
  layout: "fitColumns",
  columns: [{
      title: "Name",
      field: "name"
    },
    {
      title: "a",
      field: "a",
      editor: "input",
      cellEdited: updateSum
    },
    {
      title: "b",
      field: "b",
      editor: "input",
      cellEdited: updateSum
    },
    {
      title: "a+b",
      field: "ab",
      mutator: (value, data, type, params, component) => {
        return Number(data.a) + Number(data.b)
      }
    }
  ]
});

var tabledata = [{
    id: 1,
    name: "Oli Bob",
    a: 12,
    b: 1
  },
  {
    id: 2,
    name: "Mary May",
    a: 1,
    b: 1
  },
  {
    id: 3,
    name: "Christine Lobowski",
    a: 42,
    b: 1
  },
  {
    id: 4,
    name: "Brendon Philips",
    a: 125,
    b: 1
  },
  {
    id: 5,
    name: "Margret Marmajuke",
    a: 16,
    b: 1
  }
];

table.setData(tabledata);