JSFiddle - React, Tailwind, and code Playground

by robert_schutt

HTML

<form name="frm">
    <input name="value1" onblur="calc()">
    <select name="value2" onchange="calc()">
        <option>.001</option>
        <option>.005</option>
        <option>.01</option>
    </select>
    <input name="value3" onblur="calc()">
    <input name="value4" readonly="readonly">
</form>

JavaScript

function calc() {
    with (document.forms['frm']) {
        var conversion = elements['value1'].value * elements['value2'].value * elements['value3'].value;
        if(conversion < elements['value3'].value) {
          conversion = 0;
        }
        elements['value4'].value = conversion;
    }
}