<input type="text" class="js-range-slider" name="my_range" value="" />

<button>click</button>

$(".js-range-slider").ionRangeSlider({
  min: 0,
  max: 100,
  from: 10,
});
let my_range = $(".js-range-slider").data("ionRangeSlider");

let button = document.querySelector('button');
button.addEventListener('click', function() {
  my_range.update({
        from: 50
    });
})