JSFiddle - React, Tailwind, and code Playground

HTML

<label>Width</label><input type="text" id="width" />
<br>
<label>Length</label><input type="text" id="length" />
<br>
<label>Total</label><input type="text" id="total"/>
    
<button>Calculate</button>

JavaScript

function calculate()
{
    //Parse the string value into an integer
    var w = parseInt($('#width').val());
    var l = parseInt($('#length').val());
    var total1 = 2;
    var total2 = 3;
    
    //Perform IF
    //suggestion to use an If {} Else
    if((w * l) > 5)
    {
        //Set an internal value of total
        var total = total1 * (w + l);
        //Update the label's value to total
        $('#total').val(total);
    }
    if((w * l) < 5)
    {
        //Same logic as above
        var total = total2 * (w + l);
        $('#total').val(total);
    }
}

//Simple button event for testing
$('button').click(function()
                  {
                    calculate();
                  });