JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<input type="text" name="a" />
<input type="text" name="b" />
<input type="hidden" name="c" />
<input type="button" value="Click" onClick="doCalculate(this.form)" />
</form>

JavaScript

function doCalculate(theForm){
    var aVal = parseFloat(theForm.a.value);
    var bVal = parseFloat(theForm.b.value);
    var cVal = 0;
    if(!isNaN(aVal) && !isNaN(bVal)){
       cVal = Math.ceil(aVal/bVal);   
    }
    theForm.c.value = cVal;
}