downloadPdf () {
            const load = this.$loading({
                lock: true,
                text: ‘正在生成中...‘,
                spinner: ‘el-icon-loading‘,
                background: ‘rgba(0, 0, 0, 0.7)‘
            });
            let target  = this.pdf;
            console.log(target);
            // return;
            html2canvas(target, {
                useCORS: true, // 当图片是链接地址时，需加该属性，否组无法显示图片
                "imageTimeout": 0,
                ‘scale‘: 2,
                "width": 1300,
                "height": 2700,
            })
             .then(canvas => {
                load.close()
                let contentWidth = canvas.width; 
                let contentHeight = canvas.height; 
                //一页pdf显示html页面生成的canvas高度;
                let pageHeight = contentWidth / 592 * 841;
                //未生成pdf的html页面高度
                let leftHeight = contentHeight;
                //页面偏移
                let offsetX = 0;
                let offsetY = 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
                let imgWidth = 805;
                let imgHeight = 800/contentWidth * contentHeight;
                let pageData = canvas.toDataURL(‘image/jpeg‘, 1.0);
                let position = 0


                // 第一个方向,第二个单位,第三个尺寸格式
                // landscape横向
                let pdf = new jspdf(‘‘, ‘pt‘, ‘a4‘);
                //有两个高度需区分，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) {
                    pdf.addImage(pageData, ‘JPEG‘, -80, 0, imgWidth, imgHeight)
                } else {
                    while(leftHeight > 0) {
                        pdf.addImage(pageData, ‘JPEG‘, -80, position, imgWidth, imgHeight)
                        leftHeight -= pageHeight;
                        offsetX -= 592;
                        offsetY -= 841;
                        position-=841.89
                    //避免添加空白页
                    if(leftHeight > 0) {
                        pdf.addPage();
                    }
                    }
               }
               let name = ‘导出后的文件名.pdf‘; // 定义生成的pdf的文件名字
               pdf.save(name);
            });