JSFiddle - React, Tailwind, and code Playground

HTML

<button id="m">one</button>
<button id="n">two</button>

<p>Some text here</p>

JavaScript

if (localStorage.fontSize)
{
    $('p').css('fontSize', localStorage.fontSize);
}

$("#m").click(function () {
    $("p").css("font-size", "150%");
    localStorage.fontSize = '150%';
});

$("#n").click(function () {
    $("p").css("font-size", "100%");
    localStorage.fontSize = '100%';
});