JSFiddle - React, Tailwind, and code Playground

HTML

<input type='text' id='iText' value='toto' />
    <input type="button" onclick="javascript:showSelected();" value="OK"/>

JavaScript

function showSelected() {
var regExNumberWith2Decimals = new RegExp("^[0-9]+(\.[0-9]{1,2})?$");                
    alert(regExNumberWith2Decimals.test(iText.text));
}