纯前端html导出pdf--分页 --html2canvas+jsPDF

一. 安装插件

npm install html2canvas --save

npm install jspdf --save

二. 封装方法 htmlToPdf.js

import html2canvas from 'html2canvas';
import JsPDF from 'jspdf';

/**
 * @param  ele          要生成 pdf 的DOM元素（容器）
 * @param  padfName     PDF文件生成后的文件名字
 * */
function downloadPDF(ele, pdfName){

    let eleW = ele.offsetWidth;// 获得该容器的宽
    let eleH = ele.offsetHeight;// 获得该容器的高


    let eleOffsetTop = ele.offsetTop;  // 获得该容器到文档顶部的距离
    let eleOffsetLeft = ele.offsetLeft; // 获得该容器到文档最左的距离

    var canvas = document.createElement("canvas");
    var abs = 0;

    let win_in = document.documentElement.clientWidth || document.body.clientWidth; // 获得当前可视窗口的宽度（不包含滚动条）
    let win_out = window.innerWidth; // 获得当前窗口的宽度（包含滚动条）

    if(win_out>win_in){
        // abs = (win_o - win_i)/2;    // 获得滚动条长度的一半
        abs = (win_out - win_in)/2;    // 获得滚动条宽度的一半
        // console.log(a, '新abs');
    }

    canvas.width = eleW * 2;    // 将画布宽&&高放大两倍
    canvas.height = eleH * 2;


    var context = canvas.getContext("2d");

    context.scale(2, 2);

    context.translate(-eleOffsetLeft -abs, -eleOffsetTop);
    // 这里默认横向没有滚动条的情况，因为offset.left(),有无滚动条的时候存在差值，因此
    // translate的时候，要把这个差值去掉

    //  解决分页内容被切割问题
    let pageHeightNum = canvas.width / 2 / 592.28 * 841.89
    let lableListID = document.getElementsByClassName('target-node-item')
    for (let i = 0; i < lableListID.length; i++) {
        let multiple = Math.ceil((lableListID[i].offsetTop + lableListID[i].offsetHeight) / pageHeightNum)
        if (isSplit(lableListID, i, multiple * pageHeightNum)) {
        let divParent = lableListID[i].parentNode // 获取该div的父节点
        let newNode = document.createElement('div')
        newNode.className = 'seatDiv'
        newNode.style.background = '#ffffff'
        let _H = multiple * pageHeightNum - (lableListID[i].offsetTop + lableListID[i].offsetHeight)
        newNode.style.height = _H + 50 + 'px'
        let next = lableListID[i].nextSibling // 获取div的下一个兄弟节点
        // 判断兄弟节点是否存在
        if (next) {
            // 存在则将新节点插入到div的下一个兄弟节点之前，即div之后
            divParent.insertBefore(newNode, next)
        } else {
            // 不存在则直接添加到最后,appendChild默认添加到divParent的最后
            divParent.appendChild(newNode)
        }
        }
    }

    html2canvas( ele, {
        dpi: 300,
        // allowTaint: true,  //允许 canvas 污染， allowTaint参数要去掉，否则是无法通过toDataURL导出canvas数据的
        useCORS:true  //允许canvas画布内 可以跨域请求外部链接图片, 允许跨域请求。
    } ).then( (canvas)=>{

        var contentWidth = canvas.width;
        var contentHeight = canvas.height;
        //一页pdf显示html页面生成的canvas高度;
        var pageHeight = contentWidth / 592.28 * 841.89;
        //未生成pdf的html页面高度
        var leftHeight = contentHeight;
        //页面偏移
        var position = 0;
        //a4纸的尺寸[595.28,841.89]，html页面生成的canvas在pdf中图片的宽高
        var imgWidth = 595.28;
        var imgHeight = 595.28/contentWidth * contentHeight;

        var pageData = canvas.toDataURL('image/jpeg', 1.0);

        var pdf = new JsPDF('', 'pt', 'a4');

        //有两个高度需要区分，一个是html页面的实际高度，和生成pdf的页面高度(841.89)
        //当内容未超过pdf一页显示的范围，无需分页
        if (leftHeight < pageHeight) {
            //在pdf.addImage(pageData, 'JPEG', 左，上，宽度，高度)设置在pdf中显示；
            pdf.addImage(pageData, 'JPEG', 0, 0, imgWidth, imgHeight);
            // pdf.addImage(pageData, 'JPEG', 20, 40, imgWidth, imgHeight);
        } else {    // 分页
            while(leftHeight > 0) {
                pdf.addImage(pageData, 'JPEG', 0, position, imgWidth, imgHeight);
                leftHeight -= pageHeight;
                position -= 841.89;
                //避免添加空白页
                if(leftHeight > 0) {
                    pdf.addPage();
                }
            }
        }

        let delArr = document.getElementsByClassName('seatDiv')
        for(let i = delArr.length - 1; i >= 0; i--) {
            if(delArr[i] && delArr[i].parentElement) {
                delArr[i].remove();
            }
        }

        //可动态生成
        pdf.save(pdfName);
    })


}

function isSplit (nodes, index, pageHeight) {
    if (nodes[index].offsetTop + nodes[index].offsetHeight < pageHeight && nodes[index + 1] && nodes[index + 1].offsetTop + nodes[index + 1].offsetHeight > pageHeight) {
      return true
    }
    return false
 }

export default {
    downloadPDF
}

三. 页面调用

<div class="examDetail">
  <el-row type="flex" justify="end" class="downloadBox">
    <div class="btn" @click="handleDown">下载PDF报告</div>
  </el-row>
  <div class="testPaperWrap" id="pdfBox">
    <div class="testPaperBox" v-for="(items, indexs) in paperArr" :key="indexs">
      <div class="target-node-item testPaperTitle">
        {{++indexs }}. {{items.topic}}
      </div>
      <div class="testPaperContent">
        <div class="target-node-item figureBox">
          <chart :options="items.chartOptions" autoresize style="width: 100%;height: 420px;"></chart>
        </div>
        <div class="target-node-item answerBox">
          <el-table
            header-cell-class-name="headerBox"
            :data="items.data"
            :span-method="objectSpanMethod"
            border
            style="width: 100%; margin-top: 20px">
            <el-table-column
              label="答案"
              prop="answerCode"
              width="180">
            </el-table-column>
            <el-table-column
              prop="title"
              label="选项">
              <template slot-scope="scope">
                <span>{{scope.row.fromCharCode}}. {{scope.row.answer}}</span>
              </template>
            </el-table-column>
            <el-table-column
              prop="selectedAnswerCount"
              label="选择">
            </el-table-column>
            <el-table-column
              label="占比">
              <template slot-scope="scope">
                <span>{{(scope.row.selectedAnswerCount / scope.row.topicSum * 100) | ratioFil}}%</span>
              </template>
            </el-table-column>
          </el-table>
        </div>
      </div>
    </div>
    <div class="testPaperBox">
      <div class="target-node-item testPaperTitle">
        分数分布图
      </div>
      <div class="target-node-item testPaperContent">
        <div class="figureBox">
          <chart :options="chartOptions" autoresize style="width: 100%;height: 420px;"></chart>
        </div>
      </div>
    </div>
  </div>
</div>

import htmlToPdf from '@/utils/htmlToPdf'

handleDown() {
  htmlToPdf.downloadPDF( document.getElementById('pdfBox'), '下载pdf文件名');
},