Scripts for debugging unexpected scrolling

debugScrolling.js

function debugScrolling() {
  /* eslint-disable func-names, no-debugger, no-console, prefer-rest-params */
  const fnOnScroll = function(reason) {
    console.log(reason);
    debugger;
  };
  // scrollIntoView, scrollIntoViewIfNeeded, scrollTo
  const scrollMethods = [
    'scrollIntoView',
    'scrollIntoViewIfNeeded',
    'scrollTo',
  ];
  scrollMethods.forEach(method => {
    const origin = HTMLElement.prototype[method];
    HTMLElement.prototype[method] = function() {
      fnOnScroll(method);
      origin.apply(this, arguments);
    };
  });

    const originalFocus = HTMLElement.prototype.focus;
    HTMLElement.prototype.focus = function(options) {
      if (!options || !options.preventScroll) {
        fnOnScroll('focus');
      }
      originalFocus.apply(this, arguments);
    };

  const originalScrollTop = getPropertyDescriptor(
    HTMLElement.prototype,
    'scrollTop',
  );
  Object.defineProperty(HTMLElement.prototype, 'scrollTop', {
    get() {
      return originalScrollTop.get.apply(this, arguments);
    },
    set() {
      fnOnScroll('scrollTop');
      return originalScrollTop.set.apply(this, arguments);
    },
  });

  const originalScrollTo = window.scrollTo;
  window.scrollTo = function() {
    fnOnScroll('window.scrollTop');
    return originalScrollTo.apply(this, arguments);
  };
  const originalScrollBy = window.scrollBy;
  window.scrollBy = function() {
    fnOnScroll('window.scrollBy');
    return originalScrollBy.apply(this, arguments);
  };

  function getPropertyDescriptor(object, propertyName) {
    const descriptor = Object.getOwnPropertyDescriptor(object, propertyName);
    if (!object) {
      throw new Error('descriptor not found');
    }
    if (!descriptor) {
      return getPropertyDescriptor(Object.getPrototypeOf(object), propertyName);
    }
    return descriptor;
  }
}

debugScrolling();