一个懒加载模板

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参考 jekyll 主题 maximevaillancourt/digital-garden-jekyll-template 笔记图谱懒加载的 实现。

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<div id="test">
  模块加载中……
</div>

<script>
  let flag = true;

  window.addEventListener("load", () => {
    assertThenLoad();
  });
  
  window.addEventListener("scroll", () => {
    assertThenLoad();
  });
  
  function assertThenLoad(){
    if (canLoad()) {
      loadModule();
    }
  }
  
  function canLoad(){
    return  document.getElementById("test").getBoundingClientRect().top
      < window.innerHeight
      && flag;
  }
  
  function loadModule() {
    var oScript = document.createElement("script");

    oScript.type = "text/javascript";
    oScript.src = "https://leay.net/testmodule.js"; //需要懒加载的资源
    document.body.appendChild(oScript);

    oScript.onload = () => {
      init();// 资源加载逻辑
    };
    flag = false;
  }
</script>

比如本站 valine 评论区懒加载如下：

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<div style="text-align: center; margin-top: 10px" id="load-comment">
  评论区加载中……
</div>
<div id="vcomments" style="margin-top: 3rem"></div>
<script>
  let commentFlag = true;

  window.addEventListener("load", () => {
    assertThenLoad();
  });
  
  window.addEventListener("scroll", () => {
    assertThenLoad();
  });
  
  function assertThenLoad(){
    if (canLoad()) {
      loadModule();
    }
  }
  
  function canLoad(){
    return  document.getElementById("vcomments").getBoundingClientRect().top
      < window.innerHeight
      && commentFlag;
  }
  
  function loadModule() {
    var oScript = document.createElement("script");

    oScript.type = "text/javascript";
    oScript.src = "//unpkg.com/valine/dist/Valine.min.js";
    document.body.appendChild(oScript);

    oScript.onload = () => {
      new Valine({
        el: "#vcomments",
        appId: "app-id",
        appKey: "app-key",
      });
      document.getElementById("load-comment").style.display = "none";
    };
    commentFlag = false;
  }
</script>