前端vue实现打印、下载

分享一下几个后台管理系统比较常用的插件：下载、打印

html2canvas介绍

html2canvas是在浏览器上对网页进行截图操作，实际上是操作DOM，这个插件也有好长时间了，比较稳定，目前使用还没有遇到什么bug

jspdf介绍

如果下载出来是pdf文件，可以加上jspdf插件，会先通过html2canvas把页面转化成base64图片，再通过jspdf导出

安装

npm i html2canvas jspdf
或
yarn add html2canvas jspdf

使用

 style="padding-right: 0.1px;">import html2canvas from "html2canvas"</span><br><span role="presentation" style="padding-right: 0.1px;">import JSPDF from "jspdf"</span><br><span role="presentation" style="padding-right: 0.1px;">export default {</span><br><span role="presentation" style="padding-right: 0.1px;"> methods:{</span><br><span role="presentation" style="padding-right: 0.1px;">  toPdfFn(){</span><br><span role="presentation" style="padding-right: 0.1px;">   this.htmlToPdf('文件名','时间')</span><br><span role="presentation" style="padding-right: 0.1px;">  },</span><br><span role="presentation" style="padding-right: 0.1px;">  htmlToPdf(name,time){</span><br><span role="presentation" style="padding-right: 0.1px;">      let element = this.$refs.toPdf</span><br><span role="presentation" style="padding-right: 0.1px;">      html2canvas(element, {</span><br><span role="presentation" style="padding-right: 0.1px;">        logging: false</span><br><span role="presentation" style="padding-right: 0.1px;">      }).then(function(canvas) {</span><br><span role="presentation" style="padding-right: 0.1px;">        let pdf = new JSPDF("p", "mm", "a4") // A4纸，纵向</span><br><span role="presentation" style="padding-right: 0.1px;">        let ctx = canvas.getContext("2d")</span><br><span role="presentation" style="padding-right: 0.1px;">        let a4w = 190;</span><br><span role="presentation" style="padding-right: 0.1px;">        let a4h = 277 // A4大小，210mm x 297mm，四边各保留20mm的边距，显示区域190x277</span><br><span role="presentation" style="padding-right: 0.1px;">        let imgHeight = Math.floor(a4h * canvas.width / a4w) // 按A4显示比例换算一页图像的像素高度</span><br><span role="presentation" style="padding-right: 0.1px;">        let renderedHeight = 0</span><br><span role="presentation" style="padding-right: 0.1px;">        while (renderedHeight < canvas.height) {</span><br><span role="presentation" style="padding-right: 0.1px;">          let page = document.createElement("canvas")</span><br><span role="presentation" style="padding-right: 0.1px;">          page.width = canvas.width</span><br><span role="presentation" style="padding-right: 0.1px;">          page.height = Math.min(imgHeight, canvas.height - renderedHeight) // 可能内容不足一页</span><br><span role="presentation" style="padding-right: 0.1px;"><span cm-text=""></span></span><br><span role="presentation" style="padding-right: 0.1px;">          // 用getImageData剪裁指定区域，并画到前面创建的canvas对象中</span><br><span role="presentation" style="padding-right: 0.1px;">          page.getContext("2d").putImageData(ctx.getImageData(0, renderedHeight, canvas.width, Math.min(imgHeight,</span><br><span role="presentation" style="padding-right: 0.1px;">            canvas.height - renderedHeight)), 0, 0)</span><br><span role="presentation" style="padding-right: 0.1px;">          pdf.addImage(page.toDataURL("image/jpeg", 1.0), "JPEG", 10, 10, a4w, Math.min(a4h, a4w * page.height /</span><br><span role="presentation" style="padding-right: 0.1px;">            page.width)) // 添加图像到页面，保留10mm边距</span><br><span role="presentation" style="padding-right: 0.1px;"><span cm-text=""></span></span><br><span role="presentation" style="padding-right: 0.1px;">          // 如果后面还有内容，添加一个空页</span><br><span role="presentation" style="padding-right: 0.1px;">          renderedHeight += imgHeight</span><br><span role="presentation" style="padding-right: 0.1px;">          if (renderedHeight < canvas.height) {</span><br><span role="presentation" style="padding-right: 0.1px;">            pdf.addPage()</span><br><span role="presentation" style="padding-right: 0.1px;">          }</span><br><span role="presentation" style="padding-right: 0.1px;">        }</span><br><span role="presentation" style="padding-right: 0.1px;">        pdf.save(name + time)</span><br><span role="presentation" style="padding-right: 0.1px;">      })</span><br><span role="presentation" style="padding-right: 0.1px;">    }</span><br><span role="presentation" style="padding-right: 0.1px;"> }</span><br><span role="presentation" style="padding-right: 0.1px;">}</span><br><span role="presentation" style="padding-right: 0.1px;">

注意点： 1、能使用ref来获取html结构就用ref，尽量不使用id。如果使用的地方比较多可以挂载到vue实例上 2、导出的pdf空白情况：检查dom结构有没有获取到，还有就是css样式要写在导出区域内的元素中

printjs介绍

之前是使用vue-print-nb插件的，但是这个插件有点猫病，有时候会出现样式跨域的问题，有时候又正常，后面在GitHub上找到的一个，用到现在也没出现过什么问题

在utils文件里面创建一个print.js文件

// 打印类属性、方法定义
/* eslint-disable */
const Print = function (dom, options) {
  if (!(this instanceof Print)) return new Print(dom, options);

  this.options = this.extend({
    'noPrint': '.no-print'
  }, options);

  if ((typeof dom) === "string") {
    this.dom = document.querySelector(dom);
  } else {
    this.isDOM(dom)
    this.dom = this.isDOM(dom) ? dom : dom.$el;
  }

  this.init();
};
Print.prototype = {
  init: function () {
    var content = this.getStyle() + this.getHtml();
    this.writeIframe(content);
  },
  extend: function (obj, obj2) {
    for (var k in obj2) {
      obj[k] = obj2[k];
    }
    return obj;
  },

  getStyle: function () {
    var str = "",
      styles = document.querySelectorAll('style,link');
    for (var i = 0; i < styles.length; i++) {
      str += styles[i].outerHTML;
    }
    str += " + (this.options.noPrint ? this.options.noPrint : '.no-print') + "{display:none;}";

    return str;
  },

  getHtml: function () {
    var inputs = document.querySelectorAll('input');
    var textareas = document.querySelectorAll('textarea');
    var selects = document.querySelectorAll('select');

    for (var k = 0; k < inputs.length; k++) {
      if (inputs[k].type == "checkbox" || inputs[k].type == "radio") {
        if (inputs[k].checked == true) {
          inputs[k].setAttribute('checked', "checked")
        } else {
          inputs[k].removeAttribute('checked')
        }
      } else if (inputs[k].type == "text") {
        inputs[k].setAttribute('value', inputs[k].value)
      } else {
        inputs[k].setAttribute('value', inputs[k].value)
      }
    }

    for (var k2 = 0; k2 < textareas.length; k2++) {
      if (textareas[k2].type == 'textarea') {
        textareas[k2].innerHTML = textareas[k2].value
      }
    }

    for (var k3 = 0; k3 < selects.length; k3++) {
      if (selects[k3].type == 'select-one') {
        var child = selects[k3].children;
        for (var i in child) {
          if (child[i].tagName == 'OPTION') {
            if (child[i].selected == true) {
              child[i].setAttribute('selected', "selected")
            } else {
              child[i].removeAttribute('selected')
            }
          }
        }
      }
    }

    return this.dom.outerHTML;
  },

  writeIframe: function (content) {
    var w, doc, iframe = document.createElement('iframe'),
      f = document.body.appendChild(iframe);
    iframe.id = "myIframe";
    //iframe.style = "position:absolute;width:0;height:0;top:-10px;left:-10px;";
    iframe.setAttribute('style', 'position:absolute;width:0;height:0;top:-10px;left:-10px;');
    w = f.contentWindow || f.contentDocument;
    doc = f.contentDocument || f.contentWindow.document;
    doc.open();
    doc.write(content);
    doc.close();
    var _this = this
    iframe.onload = function(){
      _this.toPrint(w);
      setTimeout(function () {
        document.body.removeChild(iframe)
      }, 100)
    }
  },

  toPrint: function (frameWindow) {
    try {
      setTimeout(function () {
        frameWindow.focus();
        try {
          if (!frameWindow.document.execCommand('print', false, null)) {
            frameWindow.print();
          }
        } catch (e) {
          frameWindow.print();
        }
        frameWindow.close();
      }, 10);
    } catch (err) {
      console.log('err', err);
    }
  },
  isDOM: (typeof HTMLElement === 'object') ?
    function (obj) {
      return obj instanceof HTMLElement;
    } :
    function (obj) {
      return obj && typeof obj === 'object' && obj.nodeType === 1 && typeof obj.nodeName === 'string';
    }
};
const MyPlugin = {}
MyPlugin.install = function (Vue, options) {
  // 4. 添加实例方法
  Vue.prototype.$print = Print
}
export default MyPlugin

printjs源码在这里

在main.js中注册

  import Vue from "vue";
  import print from "./src/utils/print.js";
  Vue.use(print)

在需要的地方使用

><br><span role="presentation" style="padding-right: 0.1px;">export default {</span><br><span role="presentation" style="padding-right: 0.1px;">  methods: {</span><br><span role="presentation" style="padding-right: 0.1px;">    printFn() {</span><br><span role="presentation" style="padding-right: 0.1px;">      //传入dom结构即可</span><br><span role="presentation" style="padding-right: 0.1px;">      this.$print(this.$refs.print);</span><br><span role="presentation" style="padding-right: 0.1px;">    },</span><br><span role="presentation" style="padding-right: 0.1px;">  },</span><br><span role="presentation" style="padding-right: 0.1px;">};</span><br><span role="presentation" style="padding-right: 0.1px;">

><br><span role="presentation" style="padding-right: 0.1px;">@media print {</span><br><span role="presentation" style="padding-right: 0.1px;">  @page {</span><br><span role="presentation" style="padding-right: 0.1px;">    size: auto; //打印可以选择布局：横向，纵向</span><br><span role="presentation" style="padding-right: 0.1px;">    // size: landscape;//横向</span><br><span role="presentation" style="padding-right: 0.1px;">    // size: portrait;//纵向</span><br><span role="presentation" style="padding-right: 0.1px;">    margin: 23.5mm; //默认边距</span><br><span role="presentation" style="padding-right: 0.1px;">  }</span><br><span role="presentation" style="padding-right: 0.1px;">}</span><br><span role="presentation" style="padding-right: 0.1px;">

注意：需使用ref获取dom节点，若直接通过id或class获取则webpack打包部署后打印内容为空

指定不打印区域 方法

方法一. 添加no-print样式类

方法二. 自定义类名

作者：搬砖小能手丶
来源：juejin.cn/post/7131702669852278814