115 lines
5.2 KiB
JavaScript
115 lines
5.2 KiB
JavaScript
import jsPDF from 'jspdf'
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import html2canvas from 'html2canvas'
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/*
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* 使用说明
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* ele:需要导出pdf的容器元素(dom节点 不是id)
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* pdfFileName: 导出文件的名字 通过调用outPutPdfFn方法也可传参数改变
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* splitClassName: 避免分段截断的类名 当pdf有多页时需要传入此参数 , 避免pdf分页时截断元素 如表格<tr class="itemClass"></tr>
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* 调用方式 先 let pdf = new PdfLoader(ele, 'pdf' ,'itemClass');
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* 若想改变pdf名称 pdf.outPutPdfFn(fileName); outPutPdfFn方法返回一个promise 可以使用then方法处理pdf生成后的逻辑
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* */
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class PdfLoader {
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constructor(ele, pdfFileName, splitClassName) {
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this.ele = ele
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this.pdfFileName = pdfFileName
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this.splitClassName = splitClassName
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this.A4_WIDTH = 595
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this.A4_HEIGHT = 842
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}
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async getPDF(resolve) {
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const ele = this.ele;
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let eleme = this.ele;
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// eleme.style.width="800px";
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const pdfFileName = this.pdfFileName
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const eleW = ele.offsetWidth// 获得该容器的宽
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const eleH = ele.scrollHeight;// 获得该容器的高
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const eleOffsetTop = ele.offsetTop// 获得该容器到文档顶部的距离
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const eleOffsetLeft = ele.offsetLeft// 获得该容器到文档最左的距离
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const canvas = document.createElement('canvas')
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canvas.width = eleW * 3// 将画布宽&&高放大两倍
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canvas.height = eleH * 3
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const context = canvas.getContext('2d')
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context.scale(3,3) // 增强图片清晰度
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context.translate(-eleOffsetLeft , -eleOffsetTop)
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html2canvas(eleme, {
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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。
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}).then(async canvas => {
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const contentWidth = canvas.width
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const contentHeight = canvas.height
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// 一页pdf显示html页面生成的canvas高度;
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const pageHeight = (contentWidth / this.A4_WIDTH) * this.A4_HEIGHT // 这样写的目的在于保持宽高比例一致 pageHeight/canvas.width = a4纸高度/a4纸宽度// 宽度和canvas.width保持一致
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// 未生成pdf的html页面高度
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let leftHeight = contentHeight
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// 页面偏移
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let position = 20
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// a4纸的尺寸[595,842],单位像素，html页面生成的canvas在pdf中图片的宽高
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const imgWidth = this.A4_WIDTH - 40 // -10为了页面有右边距
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const imgHeight = (this.A4_WIDTH / contentWidth) * contentHeight
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const pageData = canvas.toDataURL('image/jpeg', 1.0)
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const pdf = jsPDF('', 'pt', 'a4')
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// 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)
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// 当内容未超过pdf一页显示的范围，无需分页
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if (leftHeight < pageHeight) {
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// 在pdf.addImage(pageData, 'JPEG', 左，上，宽度，高度)设置在pdf中显示；
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pdf.addImage(pageData, 'JPEG', 20, 20, imgWidth, imgHeight)
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} else {
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// 分页
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while (leftHeight > 0) {
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pdf.addImage(pageData, 'JPEG', 20, position, imgWidth, imgHeight)
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leftHeight -= pageHeight
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position -= this.A4_HEIGHT
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// 避免添加空白页
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if (leftHeight > 0) {
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pdf.addPage()
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}
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}
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}
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pdf.save(pdfFileName + '.pdf', { returnPromise: true }).then(() => {
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// 去除添加的空div 防止页面混乱
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const doms = document.querySelectorAll('.emptyDiv')
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for (let i = 0; i < doms.length; i++) {
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doms[i].remove()
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}
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})
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this.ele.style.height = ''
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resolve()
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})
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}
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//此方法是防止（图表之类）内容因为A4纸张问题被截断
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async outPutPdfFn(pdfFileName) {
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return new Promise((resolve, reject) => {
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this.ele.style.height = 'initial'
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pdfFileName ? this.pdfFileName = pdfFileName : null
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const target = this.ele
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const pageHeight = target.scrollWidth / this.A4_WIDTH * this.A4_HEIGHT
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// 获取分割dom，此处为class类名为item的dom
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const domList = document.getElementsByClassName(this.splitClassName)
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// 进行分割操作，当dom内容已超出a4的高度，则将该dom前插入一个空dom，把他挤下去，分割
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let pageNum = 1 // pdf页数
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const eleBounding = this.ele.getBoundingClientRect()
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for (let i = 0; i < domList.length; i++) {
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const node = domList[i]
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const bound = node.getBoundingClientRect()
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const offset2Ele = bound.top - eleBounding.top
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const currentPage = Math.ceil((bound.bottom - eleBounding.top) / pageHeight) // 当前元素应该在哪一页
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if (pageNum < currentPage) {
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pageNum++
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const divParent = domList[i].parentNode // 获取该div的父节点
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const newNode = document.createElement('div')
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newNode.className = 'emptyDiv'
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newNode.style.background = 'white'
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newNode.style.height = (pageHeight * (pageNum - 1) - offset2Ele + 30) + 'px' // +30为了在换下一页时有顶部的边距
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newNode.style.width = '100%'
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divParent.insertBefore(newNode, node) //在每一个节点前面插入一个空的新节点，防止内容被分割截断
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}
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}
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// 异步函数，导出成功后处理交互
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this.getPDF(resolve, reject)
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})
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}
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}
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export default PdfLoader
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