JSFiddle - React, Tailwind, and code Playground

HTML

Napíš číslo: <input type="text" id="a" value="1.12"><br>
<button onclick="myFunction(document.getElementById('a').value)">Vyskúšaj</button>
<p id="demo"></p>

<script>
function myFunction(value) {
    var num = Number(value); 
    var str = num.toFixed(2);
    while (str.length < 5) str = "0" + str;
    document.getElementById("demo").innerHTML = str ;
}
</script>