JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mydiv" data-test='{"1":"apple", "2":"banana"}'>Custom Data</div>

JavaScript

$('#mydiv').data('test')["1"] = "pear";
alert($('#mydiv').data('test')["1"]);
$('#mydiv').attr('data-test', JSON.stringify($('#mydiv').data('test')));