The Code

function getValues(){
    let startValue = document.getElementById('startValue').value;
    let endValue = document.getElementById('endValue').value;

    startValue = parseInt(startValue);
    endValue = parseInt(endValue);

    if (Number.isInteger(startValue) && Number.isInteger(endValue)){
        let numbersArray = generateNumbers(startValue, endValue);
        displayNumbers(numbersArray);
    } else {
        Swal.fire(
            {
                icon: 'error',
                title: 'You goofed it...',
                text: 'Only integers are allowed for this input.',
            }
        );
    }

}

function generateNumbers(start, end){
    let numbers = [];

    for(let value = start; value<= end; value++){
        numbers.push(value);
    }

    return numbers;
}

function displayNumbers(numbersArray){
    let tableBody = document.getElementById('results');

    let tableHtml = "";

    for(let index = 0; index < numbersArray.length; index++){
        let value = numbersArray[index];
        let className = '';
        if (value % 2 == 0){
            className = 'even';
        }
        else {
            className = 'odd';
        }

        if (index % 5 == 0){
            tableHtml += '';
        }

        let tableRow = `${value}`;

        tableHtml = tableHtml + tableRow;

        if ((index + 1) % 5 == 0) {
            tableHtml += '';
        }
    }

    tableBody.innerHTML = tableHtml;
}