chore: add lazyLoad

Author: Simon he

src/lazyLoad.ts

@@ -0,0 +1,26 @@
+import { isArray } from "./isArray";
+import { isStr } from "./isStr";
+export function lazyLoad(imgList: any, root: Element, rootMargin: string = '0px 0px 200px 0px', threshold: any): void {
+  if (isStr(imgList))
+    imgList = document.querySelectorAll(imgList);
+  if (imgList.length !== undefined)
+    imgList = [...imgList]
+  const observer = new IntersectionObserver(
+    (entries, observer) => {
+      entries.forEach(entry => {
+        /* 替换属性 */
+        console.log(entry.isIntersecting)
+        if (entry.isIntersecting) {
+          (entry.target as HTMLImageElement).src = (entry.target as any).dataset.src;
+          observer.unobserve(entry.target);
+        }
+      });
+    },
+    { rootMargin, root, threshold });
+  if (isArray(imgList))
+    (imgList as Element[]).forEach(img => observer.observe(img));
+  else observer.observe(imgList as Element);
+}
+
+
+