2020.1.20 更新：

Vue 组件发布到 npm，安装：

npm i vue-image-pdf-uploader

HTML 代码：

<div id="root">
  <div class="main-container">
    <div class="image-container">
      <div class="click-to-upload" v-if="!(imgList.length | pdfList.length)" @click="addFilesClick">点击添加文件</div>

      <div class="image-wrap" v-for="(image, index) in imgList">
        <img class="delete-icon" src="/public/images/www/icon/delete.png" @click="deleteImg(index)" alt="">
        <img class="portfolio-image" :src="image.file.src" alt="">
      </div>

      <div class="pdf-wrap" v-for="(pdf, index) in pdfList">
      <img class="delete-icon" src="/public/images/www/icon/delete.png" @click="deletePdf(index)" alt="">
      <img class="pdf-icon" src="/public/images/www/icon/file_pdf.png" alt="">
      <span class="pdf-name" v-text="pdf.file.name"></sapn>
    </div>
    </div>

    <input @change="fileChange($event)" type="file" id="upload_file" multiple style="display: none"/>
    <div class="img-count">共 <span v-text="imgList.length + pdfList.length"></span> 个文件 (<span v-text="formattedSize"></span>)
  {# 已上传 {{ count }} 个 #}</div>
    <span v-if="imgList.length | pdfList.length" class="continue-to-upload" @click="addFilesClick">继续添加</span>
  </div>

这里的 input 元素是隐藏的，在 div.click-to-upload 元素上绑定事件 addFilesClick，方法内获取 input 元素的 id 然后绑定 input 的 click 事件。

JavaScript 代码：

import Vue from 'vue';
import 'whatwg-fetch';

let vm = new Vue({
    el: '#root',
    data: {
        imgList: [],
        size: 0,
        formattedSize: '0 B',
        pdfList: [],
        name: '',
        email: '',
        tel: '',
    },

    methods: {
        addFilesClick() {
            document.getElementById('upload_file').click();
        },

        fileChange(event) {
      let files = event.target.files;
      for (let i = 0; i < files.length; i++) {
        this.addFile(files[i]);
      }
    },

        addFile(file) {
            //统计文件 size
            this.size = this.size + file.size;
            this.calculateFileSize(this.size);

            //1. 如果是图片文件
            if (file.type.indexOf('image') >= 0) {
                let reader = new FileReader();
                let image = new Image();
                let _this = this;
                reader.readAsDataURL(file);
                reader.onload = function() {
                    file.src = this.result;
                    image.onload = function() {
                        let width = image.width;
                        let height = image.height;
                        file.width = width;
                        file.height = height;
                        _this.imgList.push({ file });
                    };
                    image.src = file.src;
                };
            }

            //2. 如果是 pdf 文件
            if (file.type.indexOf('pdf') >= 0) {
                this.pdfList.push({ file });
            }
        },

        deleteImg(index) {
            //重新统计 file size
            this.size = this.size - this.imgList[index].file.size;
            this.calculateFileSize(this.size);
            this.imgList.splice(index, 1);
        },

        deletePdf(index) {
            //重新统计 file size
            this.size = this.size - this.pdfList[index].file.size;
            this.calculateFileSize(this.size);
            this.pdfList.splice(index, 1);
        },

        // file size 单位转换
        calculateFileSize(bytes) {
            let _this = this;
            if (bytes === 0) _this.formattedSize = '0 B';
            else {
                let k = 1024,
                    unit = ['B', 'KB', 'MB'],
                    i = Math.floor(Math.log(bytes) / Math.log(k));
                let result = (bytes / Math.pow(k, i)).toPrecision(3) + ' ' + unit[i];
                _this.formattedSize = result;
            }
        },

        submitFiles() {
            //获取页面最终保留的 files' name
            let imgList = this.imgList;
            let fileList = [];
            for (let i = 0; i < imgList.length; i++) {
                fileList.push(imgList[i].file.name);
            }
           .....
    },
});

点击确认上传之前，图片是暂存在本地一个临时文件夹中的，其中包含了所有文件，也就是说前台页面删除了，临时文件夹下还保留着。所以最后需要获取下前台页面中保留的文件名称，与临时文件夹下的文件进行 match，如果匹配则提交后台数据库。

CSS 代码：

.main-container {
  min-height: 120px;
  height: auto;
  width: 720px;
  position: relative;
}

.image-container {
  width: 720px;
  min-height: 110px;
  height: auto;
  display: flex;
  flex-wrap: wrap;
  text-align: center;
  line-height: 120px;
  border-bottom: 1px solid #000000;
  padding-top: 10px;
}

.click-to-upload {
  color: orangered;
  text-decoration: underline;
  text-decoration-color: orangered;
  width: 100%;
  cursor: pointer;
  line-height: 90px;
}

.image-wrap,
.pdf-wrap {
  width: 95px;
  height: 120px;
  overflow: hidden;
  position: relative;
  margin-right: 25px;
  margin-bottom: 30px;
  text-align: center;
  line-height: 120px;
}

.pdf-wrap {
  border: #585858 1px solid;
}

.pdf-wrap:hover .delete-icon {
  display: block;
}

.pdf-icon {
  width: 40px;
  height: 45px;
  position: absolute;
  top: 20px;
  left: 35px;
}

.portfolio-image {
  width: auto;
  height: auto;
  vertical-align: middle;
  // max-width: 100%;
  max-height: 100%;
}

.delete-icon {
  width: 20px;
  height: 20px;
  position: absolute;
  display: none;
  right: 0;
  top: 0;
}

.image-wrap:hover .delete-icon {
  display: block;
}

.continue-to-upload {
  width: 80px;
  line-height: 60px;
  position: absolute;
  right: 30px;
  text-decoration: underline;
  cursor: pointer;
}

.img-count {
  line-height: 60px;
  display: inline;
}

.btn {
  display: block;
}

.pdf-name {
  position: relative;
  bottom: -25px;
  font-size: 12px;
}

.submit {
  cursor: pointer;
  background-color: #e3e4e5;
  text-decoration: underline;
}

.underline {
  text-decoration: underline;
}