npm install --save html2canvas

html2canvas(document.body}).then(function(canvas) {
    document.body.appendChild(canvas);
});

npm install jspdf --save

// jsPDF 下載文本圖片PDF
const downLoadPdf = () => {
  // 三個參數(shù)，第一個方向，第二個單位，第三個尺寸 'a4' = [595.28,841.89]
  const doc = new jsPDF('', 'pt', [500, 1000])

  // 字體大小
  doc.setFontSize(50)

  // 文本，左邊距，上邊距
  doc.text('Hello world!', 10, 50)

  // base64，圖片類型，左邊距，上邊距，寬度，高度
  doc.addImage(base64, 'PNG', 10, 60, 400, 200)

  doc.save('a4.pdf')
}

const downLoadPdfAutoSingle = () => {
  html2canvas(document.body, {
    scale: window.devicePixelRatio * 2, // 使用設備的像素比 * 2
  }).then(canvas => {
    // 返回圖片dataURL，參數(shù)：圖片格式和清晰度(0-1)
    const pageData = canvas.toDataURL('image/jpeg', 1.0)

    const pageWidth = canvas.width
    const pageHeight =  canvas.height
    const orientation = canvas.height >= canvas.width ? 'portrait' : 'landscape'  // portrait 表示縱向，landscape表示橫向
    const pdf = new jsPDF(orientation, 'pt', [pageWidth, pageHeight])
    
    // addImage后兩個參數(shù)控制添加圖片的尺寸，此處將頁面高度按照a4紙寬高比列進行壓縮
    pdf.addImage(
      pageData,
      'JPEG',
      0,
      0,
      pageWidth,
      pageHeight
    )
    pdf.save('下載一頁PDF（自適應紙）.pdf')
  })
}

const downLoadPdfA4Single = () => {
  html2canvas(document.body).then(canvas => {
    // 返回圖片dataURL，參數(shù)：圖片格式和清晰度(0-1)
    const pageData = canvas.toDataURL('image/jpeg', 1.0)

    // 方向縱向，尺寸ponits，紙張格式 a4 即 [595.28, 841.89]
    const A4Width = 595.28
    const A4Height = 841.89 // A4紙寬
    const pageHeight = A4Height >= A4Width * canvas.height / canvas.width ? A4Height :  A4Width * canvas.height / canvas.width
    const pdf = new jsPDF('portrait', 'pt', [A4Width, pageHeight])
    
    // addImage后兩個參數(shù)控制添加圖片的尺寸，此處將頁面高度按照a4紙寬高比列進行壓縮
    pdf.addImage(
      pageData,
      'JPEG',
      0,
      0,
      A4Width,
      A4Width * canvas.height / canvas.width,
    )
    pdf.save('下載一頁PDF（A4紙）.pdf')
  })
}

const downLoadPdfAutoMultiple = () => {
  const ele = document.body
  html2canvas(ele, {
    scale: window.devicePixelRatio * 2, // 使用設備的像素比 * 2
  }).then(canvas => {
    let position = 0 //頁面偏移
    const autoWidth = canvas.width // 一頁紙寬度
    const autoHeight = canvas.width * 1.3 // 一頁紙高度

    // 一頁PDF可顯示的canvas高度
    const pageHeight = (canvas.width * autoHeight) / autoWidth
    // 未分配到PDF的canvas高度
    let unallottedHeight = canvas.height

    // canvas對應的PDF寬高
    const imgWidth = canvas.width
    const imgHeight = canvas.height

    const pageData = canvas.toDataURL('image/jpeg', 1.0)
    const pdf = new jsPDF('', 'pt', [autoWidth, autoHeight])

    // 當canvas高度 未超過 一頁PDF可顯示的canvas高度，無需分頁
    if (unallottedHeight <= pageHeight) {
      pdf.addImage(pageData, 'JPEG', 0, 0, imgWidth, imgHeight)
      pdf.save('下載多頁PDF（自適應紙）.pdf')
      return
    }

    while (unallottedHeight > 0) {
      pdf.addImage(pageData, 'JPEG', 0, position, imgWidth, imgHeight)
      unallottedHeight -= pageHeight
      position -= autoHeight
      if (unallottedHeight > 0) {
        pdf.addPage()
      }
    }
    pdf.save('html2canvas+jsPDF下載PDF.pdf')
  })
}

const downLoadPdfA4Multiple = () => {
  const ele = document.body
  html2canvas(ele, {
    scale: 2, // 使用設備的像素比
  }).then(canvas => {
    let position = 0 //頁面偏移
    const A4Width = 595.28 // A4紙寬度
    const A4Height = 841.89 // A4紙寬

    // 一頁PDF可顯示的canvas高度
    const pageHeight = (canvas.width * A4Height) / A4Width
    // 未分配到PDF的canvas高度
    let unallottedHeight = canvas.height

    // canvas對應的PDF寬高
    const imgWidth = A4Width
    const imgHeight = (A4Width * canvas.height) / canvas.width

    const pageData = canvas.toDataURL('image/jpeg', 1.0)
    const pdf = new jsPDF('', 'pt', [A4Width, A4Height])

    // 當canvas高度 未超過 一頁PDF可顯示的canvas高度，無需分頁
    if (unallottedHeight <= pageHeight) {
      pdf.addImage(pageData, 'JPEG', 0, 0, imgWidth, imgHeight)
      pdf.save('下載多頁PDF（A4紙）.pdf')
      return
    }

    while (unallottedHeight > 0) {
      pdf.addImage(pageData, 'JPEG', 0, position, imgWidth, imgHeight)
      unallottedHeight -= pageHeight
      position -= A4Height
      if (unallottedHeight > 0) {
        pdf.addPage()
      }
    }
    pdf.save('下載多頁PDF（A4紙）.pdf')
  })
}