How can I apply this source code in page?

[Clearly ask your question.]
This is One-page scrolling code.

$w.onReady(function () {
    console.log('onready');
    const Slider = function(pages) {
    let slides = [],
        count = 0,
        current = 0,
        touchstart = 0,
        animation_state = false;
    const init = () => {
      slides = pages.children;
      count = slides.length;
      for(let i = 0; i < count; i++) {
        slides[i].style.bottom = -(i * 100) + '%';
      }
    }
    const gotoNum = (index) => {
      if((index != current) && !animation_state) {
        animation_state = true;
        setTimeout(() => animation_state = false, 500);
        current = index;
        for(let i = 0; i < count; i++) {
          slides[i].style.bottom = (current - i) * 100 + '%';
        }
      }
    }
    const gotoNext = () => current < count - 1 ? gotoNum(current + 1) : false;
    const gotoPrev = () => current > 0 ? gotoNum(current - 1) : false;
    pages.ontouchstart = (e) => touchstart = e.touches[0].screenY;
    pages.ontouchend = (e) => touchstart < e.changedTouches[0].screenY ? gotoPrev() : gotoNext();
    pages.onmousewheel = pages.onwheel = (e) => e.deltaY < 0 ? gotoPrev() : gotoNext();
    init();
  }
  let pages = $w('.pages');
  let slider = new Slider(pages)
});

It’s Not Working. What’s problem?
‘pages’ class is exists.

This url is my test page.

Product:
Wix Editor

It seems like you are attempting to do standard DOM manipulation within Page Code.

While you can use JavaScript and CSS on sites built on Studio, it is typically done through using the $w API which targets Wix Page Elements by ID or Type.