JSFiddle - React, Tailwind, and code Playground

by Matt Ball

HTML

<form action="javascript:energyCalc()" method="post">
    <p>
        Mass of BB (grammes):
    </p>
    <p>
        <input type="text" name="mass"/>
    </p>
    <p>
        Power of weapon (Feet per second):
    </p>
    <p>
        <input type="text" name="velocity"/>
    </p>
    <p>
        <input type="submit" type="submit" onclick="energyCalc()" value="Submit"/>
    </p>
    <br/>
    <p id="energy"/>
</form>

JavaScript

function energyCalc() {

    var mass = document.forms['0'].mass.value;
    var finalMass = mass * 1000;
    var velocity = document.forms['0'].velocity.value;
    var finalVelocity = velocity * 0.3048;
    var energy = (0.5 * (finalMass * (finalVelocity * finalVelocity)));

    if ((mass && velocity) != '') {
        document.getElementById("energy").innerHTML = 'Energy of weapon: ' + energy + ' Joules';
    }
    else {
        document.getElementById("energy").innerHTML = 'You must enter values in both fields!';
    }

}