word、ppt文档新增图片预览模式

jodconverter-web/src/main/resources/static/js/lazyload.js

@@ -0,0 +1,41 @@
+function isInSight(el) {
+  const bound = el.getBoundingClientRect();
+  const clientHeight = window.innerHeight;
+  //只考虑向下滚动加载
+  //const clientWidth=window.innerWeight;
+  return bound.top <= clientHeight + 100;
+}
+
+let index = 0;
+function checkImgs() {
+  const imgs = document.querySelectorAll('.my-photo');
+  for (let i = index; i < imgs.length; i++) {
+    if (isInSight(imgs[i])) {
+      loadImg(imgs[i]);
+      index = i;
+    }
+  }
+}
+
+function loadImg(el) {
+  const source = el.dataset.src;
+  el.src = source;
+}
+
+function throttle(fn, mustRun = 500) {
+  const timer = null;
+  let previous = null;
+  return function() {
+    const now = new Date();
+    const context = this;
+    const args = arguments;
+    if (!previous) {
+      previous = now;
+    }
+    const remaining = now - previous;
+    if (mustRun && remaining >= mustRun) {
+      fn.apply(context, args);
+      previous = now;
+    }
+  }
+}