详解Vue3如何优雅的加载大量图片

// 创建IntersectionObserver实例
const observer = new IntersectionObserver((entries, observer) => {
  // 遍历观察的元素
  entries.forEach(entry => {
    // 如果元素可见
    if (entry.isIntersecting) {
      // 加载图片
      const img = entry.target;
      const src = img.getAttribute('data-src');
      img.setAttribute('src', src);
      // 停止观察该元素
      observer.unobserve(img);
    }
  });
});
// 获取所有需要懒加载的图片元素
const lazyImages = document.querySelectorAll('.lazy-image');
// 观察每个图片元素
lazyImages.forEach(image => {
  observer.observe(image);
});

import { onMounted, Ref } from "vue";
const options = {
  // root: document.querySelector(".container"), // 根元素，默认为视口
  rootMargin: "0px", // 根元素的边距
  threshold: 0.5, // 可见性比例阈值
  once: true,
};
function callback(
  entries: IntersectionObserverEntry[],
  observer: IntersectionObserver
) {
  entries.forEach((entry) => {
    // 处理每个目标元素的可见性变化
    if (entry.intersectionRatio <= 0) return;
    const img: Element = entry.target;
    const src = img.getAttribute("data-src");
    img.setAttribute("src", src ?? ""); // 将真实的图片地址赋给 src 属性
    observer.unobserve(img);
  });
}
export const useInView = (ref: Ref) => {
  const observer = new IntersectionObserver(callback, options);
  onMounted(() => {
    Object.keys(ref.value).forEach((e) => observer.observe(ref.value[e]));
  });
};

<script setup lang="ts">
import { ref } from "vue";
import { useInView } from "./hooks/useInView";
const imgRef = ref(null);
useInView(imgRef);
</script>
<template>
  <h4>公众号：萌萌哒草头将军</h4>
  <div
    v-for="(_, idx) in new Array(200).fill(11)"
  >
    <img
      ref="imgRef"
      src="https://via.placeholder.com/200"
      :data-src="`https://picsum.photos/200/${180 + idx}`"
      alt="b"
    />
  </div>
</template>

img.onload = () => {
  img.setAttribute('class', 'fade-in')
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}
/* 应用淡入动画到元素 */
.fade-in {
  animation: fadeIn 0.6s ease-in;
}

import { onMounted, Ref } from "vue";
const options = {
  // root: document.querySelector(".container"), // 根元素，默认为视口
  rootMargin: "0px", // 根元素的边距
  threshold: 0.5, // 可见性比例阈值
  once: true,
};
function callback(
  entries: IntersectionObserverEntry[],
  observer: IntersectionObserver
) {
  entries.forEach((entry) => {
    if (entry.intersectionRatio <= 0) return;
    const img = entry.target as HTMLImageElement;
    const src = img.getAttribute("data-src");
    img.setAttribute("src", src ?? ""); // 将真实的图片地址赋给 src 属性
    img.onload = () => {
      img.setAttribute("class", "fade-in");
    };
    observer.unobserve(img);
  });
}
export const useInView = (ref: Ref) => {
  const observer = new IntersectionObserver(
    callback,
    options
  );
  onMounted(() => {
    Object.keys(ref.value)
      .forEach((e) => observer.observe(ref.value[e]));
  });
};

<script setup lang="ts">
import { ref } from "vue";
import { useInView } from "./hooks/useInView";
const imgRef = ref(null);
useInView(imgRef);
</script>
<template>
  <h4>公众号：萌萌哒草头将军</h4>
  <div
    v-for="(_, idx) in new Array(200).fill(11)"
    style="width: 200px height: 200px;"
  >
    <img
      ref="imgRef"
      style="height: 100%"
      src="https://via.placeholder.com/200"
      :data-src="`https://picsum.photos/200/${180 + idx}`"
      alt="b"
    />
  </div>
</template>
<style scoped>
/* 定义淡入动画 */
@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}
/* 应用淡入动画到元素 */
.fade-in {
  animation: fadeIn 0.6s ease-in;
}
</style>