[improvement] adjust utils

packages/utils/dom/scroll.ts

@@ -0,0 +1,48 @@
+type ScrollElement = HTMLElement | Window;
+
+// get nearest scroll element
+// http://w3help.org/zh-cn/causes/SD9013
+// http://stackoverflow.com/questions/17016740/onscroll-function-is-not-working-for-chrome
+export function getScrollEventTarget(element: HTMLElement, rootParent: ScrollElement = window) {
+  let node = element;
+  while (
+    node &&
+    node.tagName !== 'HTML' &&
+    node.tagName !== 'BODY' &&
+    node.nodeType === 1 &&
+    node !== rootParent
+  ) {
+    const { overflowY } = window.getComputedStyle(node);
+    if (overflowY === 'scroll' || overflowY === 'auto') {
+      return node;
+    }
+    node = <HTMLElement>node.parentNode;
+  }
+  return rootParent;
+}
+
+export function getScrollTop(element: ScrollElement): number {
+  return 'scrollTop' in element ? element.scrollTop : element.pageYOffset;
+}
+
+export function setScrollTop(element: ScrollElement, value: number) {
+  'scrollTop' in element ? (element.scrollTop = value) : element.scrollTo(element.scrollX, value);
+}
+
+export function getRootScrollTop(): number {
+  return window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0;
+}
+
+// get distance from element top to page top
+export function getElementTop(element: ScrollElement) {
+  return (
+    (element === window ? 0 : (<HTMLElement>element).getBoundingClientRect().top) +
+    getScrollTop(window)
+  );
+}
+
+export function getVisibleHeight(element: ScrollElement) {
+  return element === window
+    ? element.innerHeight
+    : (<HTMLElement>element).getBoundingClientRect().height;
+}