解决html2canvas滚动页面截图不全：通过DOM结构优化高度计算

<div class="red-div" id="pdfDom_children">  // 这里是滚动的div
      <div class="first-div"></div>
      <div class="second-div"></div>
      <div>111</div>
 </div>

<div class="red-div">
      <div id="pdfDom_children">
        <div class="first-div"></div>
        <div class="second-div"></div>
        <div>111</div>
      </div>
</div>

// 导出页面为PDF格式
import html2canvas from "html2canvas";
import JsPDF from "jspdf";
const htmlToPdf = {
  getPdf(title: string) {
    const targetDom = document.getElementById("pdfDom_children");
    html2canvas(document.querySelector("#pdfDom_children"), {
      allowTaint: true,
      backgroundColor: "white",
      useCORS: true, //支持图片跨域
      scale: 1, //设置放大的倍数
      // height: targetDom.clientHeight,  // 网上原来的设置，没用，注释掉了
      // width: targetDom.clientWidth,  // 网上原来的设置，没用，注释掉了
      // windowHeight: targetDom.clientHeight,  // 网上原来的设置，没用，注释掉了
    }).then((canvas) => {
      //内容的宽度
      const contentWidth = canvas.width;
      //内容的高度
      const contentHeight = canvas.height;
      //一页pdf显示htm1页面生成的canvas高度，a4纸的尺寸[595.28,841.89];
      const pageHeight = (contentWidth / 592.28) * 841.89;
      //未生成pdf的htm1页面高度
      let leftHeight = contentHeight;
      //页面偏移
      let position = 0;
      //a4纸的尺寸[595.28,841.89],htm1页面生成的canvas在pdf中图片的宽高
      const imgwidth = 595.28;
      const imgHeight = (592.28 / contentWidth) * contentHeight;
      //canvas转图片数据
      const pageData = canvas.toDataURL("img/jpeg", 1.0);
      //新建JSPDF对象
      const PDF = new JsPDF("", "pt", "a4");
      if (leftHeight < pageHeight) {
        PDF.addImage(pageData, "JPEG", 0, 0, imgwidth, imgHeight);
      } else {
        while (leftHeight > 0) {
          PDF.addImage(pageData, "JPEG", 0, position, imgwidth, imgHeight);
          leftHeight -= pageHeight;
          position -= 841.89;
          if (leftHeight > 0) {
            PDF.addPage();
          }
        }
      }
      console.log(pageData); //保存文件
      PDF.save(title + ".pdf");
    });
  },
};
export default htmlToPdf;