var updateSlider = document.getElementById('slider-update');
var updateSliderValue = document.getElementById('slider-update-value');

noUiSlider.create(updateSlider, {
    range: {
        'min': 0,
        'max': 40
    },
    padding: 6,
    start: 20,
    margin: 2,
    step: 2
});

updateSlider.noUiSlider.on('update', function (values, handle) {
    updateSliderValue.innerHTML = values[handle];
});