前端页面如何原样快速导出PDF?附示例

如何保持页面样式基本不变的前提下将HTML页面导出为PDF,下面提供一些示例代码,纯属个人原创,如对你有帮助请记得加关注、加收藏、点赞、转发、分享~谢谢~~
  • 基本思路:保持页面样式基本不变 , 使用 `html2canvas` 将页面转换为图片,然后再通过 `jspdf` 将图片分页导出为PDF文件(中间会遇到图片或文字等内容在分页处被切割开的问题,如何解决了?详见末尾干货)
  • 上基础代码:下面为项目中实际代码截取

这是脱离文档流的内容区域这是一行内容 , 也是最小叶子元素内容/*** 1.使用一个隐藏div装载有滚动条的div.innerHTML* 2.隐藏div使用position: absolute, z-index: -999, left: -9999px, width: 900px 控制让用户无感知* 3.根据需要覆写隐藏div内html样式(例如textarea多行显示有问题, 可以新增一个隐藏的div*包裹textarea的绑定值, 然后在打印样式中覆写样式, 隐藏textarea并显示对应div)*/handleExport() {// 下面是VUE组件内获取DOM元素代码,将内容放置到打印区(定义的隐藏DIV)中const contentRef = this.$refs.contentRef as HTMLElement;const printContainerRef = this.$refs.printContainerRef as HTMLElement;// 打印区的需额外处理绝对定位值, 调整使得第一个元素的.top值为0, 以便于页面计算printContainerRef.innerHTML = contentRef.innerHTML;// 所有叶子div元素加上 print-item 样式名, 脱离文档流的额外添加 print-out-flowhandlePrintItem(printContainerRef);// 解决多页内容可能被切割问题html2canvas(printContainerRef, {allowTaint: false, useCORS: true}).then((canvas: any) => {const contentHeight = canvas.height;const contentWidth = canvas.width;// pdf每页显示的内容高度const pageHeight = contentWidth / 595.28 * 841.89;// 未生成pdf的页面高度let offsetHeight = contentHeight;// 页面偏移值let position = 0;// a4纸的尺寸[595.28, 841.89], canvas图片按a4纸大小缩放后的宽高const imgWidth = 595.28;const imgHeight = 595.28 / contentWidth * contentHeight;const dataURL = canvas.toDataURL('image/jpeg', 1.0);const doc = new jsPDF('p', 'pt', 'a4');if (offsetHeight < pageHeight) {doc.addImage(dataURL, 'JPEG', 0, 0, imgWidth, imgHeight);} else {while (offsetHeight > 0) {doc.addImage(dataURL, 'JPEG', 0, position, imgWidth, imgHeight);offsetHeight -= pageHeight;position -= 841.89;if (offsetHeight > 0) {doc.addPage();}}}doc.save(this.generateReportFileName());printContainerRef.innerHTML = '';});}
上干货代码:上面分页导出PDF可能网上能看到类型代码,但绝对找不到下面的代码,纯手搓解决分页元素被切开问题(思路:获取自身定位,如自己刚好在被分页处,则加上一定的margin-top值将内容向下移)
/*** 处理打印元素项, 修复分页后被切割的元素 * @param printContainerRef 打印内容div容器 * @param itemClassName 打印最小元素标识类名 * @param outFlowClassName 脱离文档流的元素标识类名 */export function handlePrintItem(printContainerRef: HTMLElement,itemClassName: string = 'print-item',outFlowClassName: string = 'print-out-flow'): void {const rootClientRect = printContainerRef.getBoundingClientRect();// 初始化页面相关数据const totalHeight = rootClientRect.height;// 内容总高度const a4PageHeight = (printContainerRef.clientWidth / 595.28) * 841.89; // a4纸高度let pageNum = Math.ceil(totalHeight / a4PageHeight);// 总页数let addPageHeight = 0;// 修正被分割元素而增加的页面高度总和let currentPage = 1;// 当前正在处理切割的页面const splitItemObj: { [key: number]: HTMLElement[] } = {};// 内容中各页被切割元素存储对象const printItemNodes: NodeListOf = printContainerRef.querySelectorAll(`.${itemClassName}`);for (let item of printItemNodes) {// 如果当前页已经是最后一页, 则中断判断if (currentPage >= pageNum) {break;}// 获取元素绝对定位数据const clientRect = item.getBoundingClientRect();let top = clientRect.top;const selfHeight = clientRect.height;// 如果当前元素距离顶部高度大于当前页面页脚高度, 则开始判断下一页页脚被切割元素if (top > currentPage * a4PageHeight) {// 换页前修正上一页被切割元素addPageHeight= fixSplitItems(currentPage, a4PageHeight, splitItemObj[currentPage], outFlowClassName);pageNum = Math.ceil((totalHeightaddPageHeight) / a4PageHeight);top = item.getBoundingClientRect().top;currentPage;}// 如果元素刚好处于两页之间, 则记录该元素if (top > (currentPage - 1) * a4PageHeight && top < currentPage * a4PageHeight && topselfHeight > currentPage * a4PageHeight) {if (!splitItemObj[currentPage]) {splitItemObj[currentPage] = [];}splitItemObj[currentPage].unshift(item);// 如果当前元素是最后一个元素, 则直接处理切割元素, 否则交由处理下一页元素时再处理切割if (item === printItemNodes[printItemNodes.length - 1]) {fixSplitItems(currentPage, a4PageHeight, splitItemObj[currentPage], outFlowClassName);}}}}/*** 修复当前页所有被切割元素* @param currentPage 当前页* @param pageHeight 每页高度* @param splitElementItems 当前被切割元素数组* @param outFlowClassName 脱离文档流的样式类名*/function fixSplitItems(currentPage: number,pageHeight: number,splitElementItems: HTMLElement[],outFlowClassName: string): number {if (!splitElementItems || !splitElementItems.length) {return 0;}const yMargin = 5;// y方向距离页眉的距离const splitItemsMinTop = getSplitItemsMinTop(splitElementItems);if (!splitItemsMinTop) {return 0;}let fixHeight = currentPage * pageHeight - splitItemsMinTopyMargin;const outFlowElement = splitElementItems.find((item) => item.classList.contains(outFlowClassName));if (outFlowElement && outFlowElement.parentElement) {const parentPreviousElement = outFlowElement.parentElement.previousElementSibling as HTMLElement;fixHeight= getMarinTopNum(parentPreviousElement, outFlowElement.parentElement);outFlowElement.parentElement.style.marginTop = `${fixHeight}px`;return fixHeight;}splitElementItems.forEach((splitElement) => {splitElement.style.marginTop = `${fixHeight}px`;});return fixHeight;}/*** 获取被切割元素数组中最小高度值(如一行有多个元素被切割 , 则选出距离顶部最小的高度值)* @param splitElementItems 当前被切割元素数组*/function getSplitItemsMinTop(splitElementItems: HTMLElement[]): number | undefined {// 获取元素中最小top值作为基准进行修正let minTop: number | undefined;let minElement: HTMLElement | undefined;splitElementItems.forEach((splitElement) => {let top = splitElement.getBoundingClientRect().top;if (minTop) {minTop = top < minTop ? top : minTop;minElement = top < minTop ? splitElement : minElement;} else {minTop = top;minElement = splitElement;}});// 修正当前节点及其前面同层级节点的margin值if (minTop && minElement) {const previousElement = splitElementItems[splitElementItems.length - 1].previousElementSibling as HTMLElement;minTop -= getMarinTopNum(previousElement, minElement);}return minTop;}/*** 通过前一个兄弟元素和元素自身的位置确认一个距离顶部高度修正值* @param previousElement 前一个兄弟元素* @param curElement 当前元素*/function getMarinTopNum(previousElement: HTMLElement, curElement: HTMLElement): number {let preMarginNum = 0;let curMarginNum = 0;if (previousElement) {// 获取外联样式需要getComputedStyle(), 直接.style时对象的值都为空const previousMarginBottom = window.getComputedStyle(previousElement).marginBottom;preMarginNum = previousMarginBottom ? Number(previousMarginBottom.replace('px', '')) : 0;}const marginTop = window.getComputedStyle(curElement).marginTop;curMarginNum = marginTop ? Number(marginTop.replace('px', '')) : 0;return preMarginNum > curMarginNum ? preMarginNum : curMarginNum;}

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