element-ui Upload 上传组件源码分析笔记（转载）

简单写了部分注释，upload-dragger.vue（拖拽上传时显示此组件）、upload-list.vue（已上传文件列表）源码暂未添加多少注释，等有空再补充，先记下来…

index.vue

<script>
import UploadList from './upload-list';
import Upload from './upload';
import ElProgress from 'element-ui/packages/progress';
import Migrating from 'element-ui/src/mixins/migrating';

function noop() {}

export default {
  name: 'ElUpload',

  mixins: [Migrating],

  components: {
    ElProgress,
    UploadList,
    Upload
  },

  provide() {
    return {
      uploader: this
    };
  },

  inject: {
    elForm: {
      default: ''
    }
  },

  props: {
    action: { //必选参数，上传的地址
      type: String,
      required: true
    },
    headers: { //设置上传的请求头部
      type: Object,
      default() {
        return {};
      }
    },
    data: Object, //上传时附带的额外参数
    multiple: Boolean, //是否支持多选文件
    name: { //上传的文件字段名
      type: String,
      default: 'file'
    },
    drag: Boolean, //是否启用拖拽上传
    dragger: Boolean,
    withCredentials: Boolean, //支持发送 cookie 凭证信息
    showFileList: { //是否显示已上传文件列表
      type: Boolean,
      default: true
    },
    accept: String, //接受上传的文件类型（thumbnail-mode 模式下此参数无效）
    type: {
      type: String,
      default: 'select'
    },
    beforeUpload: Function, //上传文件之前的钩子，参数为上传的文件，若返回 false 或者返回 Promise 且被 reject，则停止上传。
    beforeRemove: Function, //删除文件之前的钩子，参数为上传的文件和文件列表，若返回 false 或者返回 Promise 且被 reject，则停止上传。
    onRemove: { //文件列表移除文件时的钩子
      type: Function,
      default: noop
    },
    onChange: { //文件状态改变时的钩子，添加文件、上传成功和上传失败时都会被调用
      type: Function,
      default: noop
    },
    onPreview: { //点击文件列表中已上传的文件时的钩子
      type: Function
    },
    onSuccess: { //文件上传成功时的钩子
      type: Function,
      default: noop
    },
    onProgress: { //文件上传时的钩子
      type: Function,
      default: noop
    },
    onError: { //文件上传失败时的钩子
      type: Function,
      default: noop
    },
    fileList: { //上传的文件列表, 例如: [{name: 'food.jpg', url: 'https://xxx.cdn.com/xxx.jpg'}]
      type: Array,
      default() {
        return [];
      }
    },
    autoUpload: { //是否在选取文件后立即进行上传
      type: Boolean,
      default: true
    },
    listType: { //文件列表的类型
      type: String,
      default: 'text' // text,picture,picture-card
    },
    httpRequest: Function, //覆盖默认的上传行为，可以自定义上传的实现
    disabled: Boolean, //是否禁用
    limit: Number, //最大允许上传个数
    onExceed: { //文件超出个数限制时的钩子
      type: Function,
      default: noop
    }
  },

  data() {
    return {
      uploadFiles: [],
      dragOver: false,
      draging: false,
      tempIndex: 1
    };
  },

  computed: {
    uploadDisabled() {
      return this.disabled || (this.elForm || {}).disabled;
    }
  },

  watch: {
    fileList: {
      immediate: true,
      handler(fileList) {
        this.uploadFiles = fileList.map(item => {
          item.uid = item.uid || (Date.now() + this.tempIndex++);
          item.status = item.status || 'success';
          return item;
        });
      }
    }
  },

  methods: {
    //文件上传之前调用的方法
    handleStart(rawFile) {
      rawFile.uid = Date.now() + this.tempIndex++;
      let file = {
        status: 'ready',
        name: rawFile.name,
        size: rawFile.size,
        percentage: 0,
        uid: rawFile.uid,
        raw: rawFile
      };
      //判断文件列表类型
      if (this.listType === 'picture-card' || this.listType === 'picture') {
        try {
          file.url = URL.createObjectURL(rawFile);
        } catch (err) {
          console.error('[Element Error][Upload]', err);
          return;
        }
      }
      this.uploadFiles.push(file);
      this.onChange(file, this.uploadFiles);
    },
    handleProgress(ev, rawFile) {
      const file = this.getFile(rawFile);
      this.onProgress(ev, file, this.uploadFiles);
      file.status = 'uploading';
      file.percentage = ev.percent || 0;
    },
    //文件上传成功后改用该方法，在该方法中调用用户设置的on-success和on-change方法，并将对应的参数传递出去
    handleSuccess(res, rawFile) {
      const file = this.getFile(rawFile);

      if (file) {
        file.status = 'success';
        file.response = res;

        this.onSuccess(res, file, this.uploadFiles);
        this.onChange(file, this.uploadFiles);
      }
    },
    //文件上传失败后改用该方法，在该方法中调用用户设置的on-error和on-change方法，并将对应的参数传递出去
    handleError(err, rawFile) {
      const file = this.getFile(rawFile);
      const fileList = this.uploadFiles;

      file.status = 'fail';

      fileList.splice(fileList.indexOf(file), 1);

      this.onError(err, file, this.uploadFiles);
      this.onChange(file, this.uploadFiles);
    },
    //文件列表移除文件时调用该方法
    handleRemove(file, raw) {
      if (raw) {
        file = this.getFile(raw);
      }
      let doRemove = () => {
        this.abort(file);
        let fileList = this.uploadFiles;
        fileList.splice(fileList.indexOf(file), 1);
        this.onRemove(file, fileList);
      };

      if (!this.beforeRemove) {
        doRemove();
      } else if (typeof this.beforeRemove === 'function') {
        const before = this.beforeRemove(file, this.uploadFiles);
        if (before && before.then) {
          before.then(() => {
            doRemove();
          }, noop);
        } else if (before !== false) {
          doRemove();
        }
      }
    },
    getFile(rawFile) {
      let fileList = this.uploadFiles;
      let target;
      fileList.every(item => {
        target = rawFile.uid === item.uid ? item : null;
        return !target;
      });
      return target;
    },
    abort(file) {
      this.$refs['upload-inner'].abort(file);
    },
    clearFiles() {
      this.uploadFiles = [];
    },
    submit() {
      this.uploadFiles
        .filter(file => file.status === 'ready')
        .forEach(file => {
          this.$refs['upload-inner'].upload(file.raw);
        });
    },
    getMigratingConfig() {
      return {
        props: {
          'default-file-list': 'default-file-list is renamed to file-list.',
          'show-upload-list': 'show-upload-list is renamed to show-file-list.',
          'thumbnail-mode': 'thumbnail-mode has been deprecated, you can implement the same effect according to this case: http://element.eleme.io/#/zh-CN/component/upload#yong-hu-tou-xiang-shang-chuan'
        }
      };
    }
  },

  beforeDestroy() {
    this.uploadFiles.forEach(file => {
      if (file.url && file.url.indexOf('blob:') === 0) {
        URL.revokeObjectURL(file.url);
      }
    });
  },

  render(h) {
    let uploadList;
    //如果用户设置showFileList为true，则显示上传文件列表
    if (this.showFileList) {
      uploadList = (
        <UploadList
          disabled={this.uploadDisabled}
          listType={this.listType}
          files={this.uploadFiles}
          on-remove={this.handleRemove}
          handlePreview={this.onPreview}>
        </UploadList>
      );
    }

    const uploadData = {
      props: {
        type: this.type,
        drag: this.drag,
        action: this.action,
        multiple: this.multiple,
        'before-upload': this.beforeUpload,
        'with-credentials': this.withCredentials,
        headers: this.headers,
        name: this.name,
        data: this.data,
        accept: this.accept,
        fileList: this.uploadFiles,
        autoUpload: this.autoUpload,
        listType: this.listType,
        disabled: this.uploadDisabled,
        limit: this.limit,
        'on-exceed': this.onExceed,
        'on-start': this.handleStart,
        'on-progress': this.handleProgress,
        'on-success': this.handleSuccess,
        'on-error': this.handleError,
        'on-preview': this.onPreview,
        'on-remove': this.handleRemove,
        'http-request': this.httpRequest
      },
      ref: 'upload-inner'
    };

    const trigger = this.$slots.trigger || this.$slots.default;
    const uploadComponent = <upload {...uploadData}>{trigger}</upload>;

    return (
      <div>
        { this.listType === 'picture-card' ? uploadList : ''}
        {
          this.$slots.trigger
            ? [uploadComponent, this.$slots.default]
            : uploadComponent
        }
        {this.$slots.tip}
        { this.listType !== 'picture-card' ? uploadList : ''}
      </div>
    );
  }
};
script>

upload.vue

<script>
import ajax from './ajax';
import UploadDragger from './upload-dragger.vue';

export default {
  inject: ['uploader'],
  components: {
    UploadDragger
  },
  props: {
    type: String,
    action: { //必选参数，上传的地址
      type: String,
      required: true
    },
    name: { //上传的文件字段名
      type: String,
      default: 'file'
    },
    data: Object, //上传时附带的额外参数
    headers: Object, //设置上传的请求头部
    withCredentials: Boolean, //支持发送 cookie 凭证信息
    multiple: Boolean, //是否支持多选文件
    accept: String, //接受上传的文件类型（thumbnail-mode 模式下此参数无效）
    onStart: Function,
    onProgress: Function, //文件上传时的钩子
    onSuccess: Function, //文件上传成功时的钩子
    onError: Function, //文件上传失败时的钩子
    beforeUpload: Function, //上传文件之前的钩子，参数为上传的文件，若返回 false 或者返回 Promise 且被 reject，则停止上传。
    drag: Boolean, //是否启用拖拽上传
    onPreview: { //点击文件列表中已上传的文件时的钩子
      type: Function,
      default: function() {}
    },
    onRemove: { //文件列表移除文件时的钩子
      type: Function,
      default: function() {}
    },
    fileList: Array, //上传的文件列表, 例如: [{name: 'food.jpg', url: 'https://xxx.cdn.com/xxx.jpg'}]
    autoUpload: Boolean, //是否在选取文件后立即进行上传
    listType: String, //文件列表的类型
    httpRequest: { //覆盖默认的上传行为，可以自定义上传的实现
      type: Function,
      default: ajax
    },
    disabled: Boolean,//是否禁用
    limit: Number,//最大允许上传个数
    onExceed: Function //文件超出个数限制时的钩子
  },

  data() {
    return {
      mouseover: false,
      reqs: {}
    };
  },

  methods: {
    isImage(str) {
      return str.indexOf('image') !== -1;
    },
    handleChange(ev) {
      const files = ev.target.files;

      if (!files) return;
      this.uploadFiles(files);
    },
    uploadFiles(files) {
      //文件超出个数限制时，调用onExceed钩子函数
      if (this.limit && this.fileList.length + files.length > this.limit) {
        this.onExceed && this.onExceed(files, this.fileList);
        return;
      }
      //将files转成数组
      let postFiles = Array.prototype.slice.call(files);
      if (!this.multiple) { postFiles = postFiles.slice(0, 1); }

      if (postFiles.length === 0) { return; }

      postFiles.forEach(rawFile => {
        this.onStart(rawFile);
        //选取文件后调用upload方法立即进行上传文件
        if (this.autoUpload) this.upload(rawFile);
      });
    },
    upload(rawFile) {
      this.$refs.input.value = null;
      //beforeUpload 上传文件之前的钩子不存在就直接调用post上传文件
      if (!this.beforeUpload) {
        return this.post(rawFile);
      }
      // beforeUpload 上传文件之前的钩子，参数为上传的文件，若返回 false 或者返回 Promise 且被 reject，则停止上传
      const before = this.beforeUpload(rawFile);
      // 在调用beforeUpload钩子后返回的是true，则继续上传
      if (before && before.then) {
        before.then(processedFile => {
          //processedFile转成对象
          const fileType = Object.prototype.toString.call(processedFile);

          if (fileType === '[object File]' || fileType === '[object Blob]') {
            if (fileType === '[object Blob]') {
              processedFile = new File([processedFile], rawFile.name, {
                type: rawFile.type
              });
            }
            for (const p in rawFile) {
              if (rawFile.hasOwnProperty(p)) {
                processedFile[p] = rawFile[p];
              }
            }
            this.post(processedFile);
          } else {
            this.post(rawFile);
          }
        }, () => {
          this.onRemove(null, rawFile);
        });
      } else if (before !== false) { //调用beforeUpload之后没有返回值，此时before为undefined，继续上传
        this.post(rawFile);
      } else {  //调用beforeUpload之后返回值为false，则不再继续上传并移除文件
        this.onRemove(null, rawFile);
      }
    },
    abort(file) {
      const { reqs } = this;
      if (file) {
        let uid = file;
        if (file.uid) uid = file.uid;
        if (reqs[uid]) {
          reqs[uid].abort();
        }
      } else {
        Object.keys(reqs).forEach((uid) => {
          if (reqs[uid]) reqs[uid].abort();
          delete reqs[uid];
        });
      }
    },
    //上传文件过程的方法
    post(rawFile) {
      const { uid } = rawFile;
      const options = {
        headers: this.headers,
        withCredentials: this.withCredentials,
        file: rawFile,
        data: this.data,
        filename: this.name,
        action: this.action,
        onProgress: e => { //文件上传时的钩子函数
          this.onProgress(e, rawFile);
        },
        onSuccess: res => { //文件上传成功的钩子函数
          //上传成功调用onSuccess方法，即index.vue中的handleSuccess方法
          this.onSuccess(res, rawFile);
          delete this.reqs[uid];
        },
        onError: err => { //文件上传失败的钩子函数
          this.onError(err, rawFile);
          delete this.reqs[uid];
        }
      };
      //httpRequest可以自定义上传文件，如果没有定义，默认通过ajax文件中的方法上传
      const req = this.httpRequest(options);
      this.reqs[uid] = req;
      if (req && req.then) {
        req.then(options.onSuccess, options.onError);
      }
    },
    handleClick() {
      //点击组件时调用input的click方法
      if (!this.disabled) {
        this.$refs.input.value = null;
        this.$refs.input.click();
      }
    },
    handleKeydown(e) {
      if (e.target !== e.currentTarget) return;
      //如果当前按下的是回车键和空格键，调用handleClick事件
      if (e.keyCode === 13 || e.keyCode === 32) {
        this.handleClick();
      }
    }
  },

  render(h) {
    let {
      handleClick,
      drag,
      name,
      handleChange,
      multiple,
      accept,
      listType,
      uploadFiles,
      disabled,
      handleKeydown
    } = this;
    const data = {
      class: {
        'el-upload': true
      },
      on: {
        click: handleClick,
        keydown: handleKeydown
      }
    };
    data.class[`el-upload--${listType}`] = true;
    return (
      //判断是否允许拖拽，允许的话显示upload-dragger组件，不允许就显示所有插槽中的节点
      <div {...data} tabindex="0" >
        {
          drag
            ? <upload-dragger disabled={disabled} on-file={uploadFiles}>{this.$slots.default}</upload-dragger>
            : this.$slots.default
        }
        <input class="el-upload__input" type="file" ref="input" name={name} on-change={handleChange} multiple={multiple} accept={accept}></input>
      </div>
    );
  }
};
script>

ajax.js
function getError(action, option, xhr) {
  let msg;
  if (xhr.response) {
    msg = `${xhr.response.error || xhr.response}`;
  } else if (xhr.responseText) {
    msg = `${xhr.responseText}`;
  } else {
    msg = `fail to post ${action} ${xhr.status}`;
  }

  const err = new Error(msg);
  err.status = xhr.status;
  err.method = 'post';
  err.url = action;
  return err;
}

function getBody(xhr) {
  const text = xhr.responseText || xhr.response;
  if (!text) {
    return text;
  }

  try {
    return JSON.parse(text);
  } catch (e) {
    return text;
  }
}
//默认的上传文件的方法
export default function upload(option) {
  //XMLHttpRequest 对象用于在后台与服务器交换数据。
  if (typeof XMLHttpRequest === 'undefined') {
    return;
  }
  //创建XMLHttpRequest对象
  const xhr = new XMLHttpRequest();
  const action = option.action; //上传的地址

  //XMLHttpRequest.upload 属性返回一个 XMLHttpRequestUpload对象，用来表示上传的进度。这个对象是不透明的，但是作为一个XMLHttpRequestEventTarget，可以通过对其绑定事件来追踪它的进度。
  if (xhr.upload) {
    //上传进度调用方法,上传过程中会频繁调用该方法
    xhr.upload.onprogress = function progress(e) {
      if (e.total > 0) {
        // e.total是需要传输的总字节，e.loaded是已经传输的字节
        e.percent = e.loaded / e.total * 100;
      }
      //调文件上传时的钩子函数
      option.onProgress(e);
    };
  }
  // 创建一个FormData 对象
  const formData = new FormData();
  //用户设置了上传时附带的额外参数时
  if (option.data) {
    Object.keys(option.data).forEach(key => {
      // 添加一个新值到 formData 对象内的一个已存在的键中，如果键不存在则会添加该键。
      formData.append(key, option.data[key]);
    });
  }

  formData.append(option.filename, option.file, option.file.name);
  //请求出错
  xhr.onerror = function error(e) {
    option.onError(e);
  };
  //请求成功回调函数
  xhr.onload = function onload() {
    if (xhr.status < 200 || xhr.status >= 300) {
      return option.onError(getError(action, option, xhr));
    }
    //调用upload.vue文件中的onSuccess方法，将上传接口返回值作为参数传递
    option.onSuccess(getBody(xhr));
  };
  //初始化请求
  xhr.open('post', action, true);

  if (option.withCredentials && 'withCredentials' in xhr) {
    xhr.withCredentials = true;
  }

  const headers = option.headers || {};

  for (let item in headers) {
    if (headers.hasOwnProperty(item) && headers[item] !== null) {
      //设置请求头
      xhr.setRequestHeader(item, headers[item]);
    }
  }
  //发送请求
  xhr.send(formData);
  return xhr;
}

upload-dragger.vue

<template>
  
  <div
    class="el-upload-dragger"
    :class="{
      'is-dragover': dragover
    }"
    @drop.prevent="onDrop"
    @dragover.prevent="onDragover"
    @dragleave.prevent="dragover = false"
  >
    <slot>slot>
  div>
template>
<script>
  export default {
    name: 'ElUploadDrag',
    props: {
      disabled: Boolean
    },
    inject: {
      uploader: {
        default: ''
      }
    },
    data() {
      return {
        dragover: false
      };
    },
    methods: {
      onDragover() {
        if (!this.disabled) {
          this.dragover = true;
        }
      },
      onDrop(e) {
        if (this.disabled || !this.uploader) return;
        //接受上传的文件类型（thumbnail-mode 模式下此参数无效），此处判断该文件是都符合能上传的类型
        const accept = this.uploader.accept;
        this.dragover = false;
        if (!accept) {
          this.$emit('file', e.dataTransfer.files);
          return;
        }
        this.$emit('file', [].slice.call(e.dataTransfer.files).filter(file => {
          const { type, name } = file;
          //获取文件名后缀，与设置的文件类型进行对比
          const extension = name.indexOf('.') > -1
            ? `.${ name.split('.').pop() }`
            : '';
          const baseType = type.replace(/\/.*$/, '');
          return accept.split(',')
            .map(type => type.trim())
            .filter(type => type)
            .some(acceptedType => {
              if (/\..+$/.test(acceptedType)) {
                //文件名后缀与设置的文件类型进行对比
                return extension === acceptedType;
              }
              if (/\/\*$/.test(acceptedType)) {
                return baseType === acceptedType.replace(/\/\*$/, '');
              }
              if (/^[^\/]+\/[^\/]+$/.test(acceptedType)) {
                return type === acceptedType;
              }
              return false;
            });
        }));
      }
    }
  };
script>

upload-list.vue

<template>
  
  <transition-group
    tag="ul"
    :class="[
      'el-upload-list',
      'el-upload-list--' + listType,
      { 'is-disabled': disabled }
    ]"
    name="el-list">
    <li
      v-for="file in files"
      :class="['el-upload-list__item', 'is-' + file.status, focusing ? 'focusing' : '']"
      :key="file.uid"
      tabindex="0"
      @keydown.delete="!disabled && $emit('remove', file)"
      @focus="focusing = true"
      @blur="focusing = false"
      @click="focusing = false"
    >
      <img
        class="el-upload-list__item-thumbnail"
        v-if="file.status !== 'uploading' && ['picture-card', 'picture'].indexOf(listType) > -1"
        :src="file.url" alt=""
      >
      <a class="el-upload-list__item-name" @click="handleClick(file)">
        <i class="el-icon-document">i>{{file.name}}
      a>
      <label class="el-upload-list__item-status-label">
        <i :class="{
          'el-icon-upload-success': true,
          'el-icon-circle-check': listType === 'text',
          'el-icon-check': ['picture-card', 'picture'].indexOf(listType) > -1
        }">i>
      label>
      <i class="el-icon-close" v-if="!disabled" @click="$emit('remove', file)">i>
      <i class="el-icon-close-tip" v-if="!disabled">{{ t('el.upload.deleteTip') }}i> 
      <el-progress
        v-if="file.status === 'uploading'"
        :type="listType === 'picture-card' ? 'circle' : 'line'"
        :stroke-width="listType === 'picture-card' ? 6 : 2"
        :percentage="parsePercentage(file.percentage)">
      el-progress>
      <span class="el-upload-list__item-actions" v-if="listType === 'picture-card'">
        <span
          class="el-upload-list__item-preview"
          v-if="handlePreview && listType === 'picture-card'"
          @click="handlePreview(file)"
        >
          <i class="el-icon-zoom-in">i>
        span>
        <span
          v-if="!disabled"
          class="el-upload-list__item-delete"
          @click="$emit('remove', file)"
        >
          <i class="el-icon-delete">i>
        span>
      span>
    li>
  transition-group>
template>
<script>
  import Locale from 'element-ui/src/mixins/locale';
  import ElProgress from 'element-ui/packages/progress';

  export default {

    name: 'ElUploadList',

    mixins: [Locale],

    data() {
      return {
        focusing: false
      };
    },
    components: { ElProgress },

    props: {
      files: {
        type: Array,
        default() {
          return [];
        }
      },
      disabled: {
        type: Boolean,
        default: false
      },
      handlePreview: Function,
      listType: String
    },
    methods: {
      parsePercentage(val) {
        return parseInt(val, 10);
      },
      handleClick(file) {
        this.handlePreview && this.handlePreview(file);
      }
    }
  };
script>

转载至
https://www.cnblogs.com/fangnianqin/archive/2019/09/02/11447906.html