vant/packages/uploader/index.js

import { use } from '../utils';

const [sfc, bem] = use('uploader');

export default sfc({
  inheritAttrs: false,

  props: {
    disabled: Boolean,
    beforeRead: Function,
    afterRead: Function,
    accept: {
      type: String,
      default: 'image/*'
    },
    resultType: {
      type: String,
      default: 'dataUrl'
    },
    maxSize: {
      type: Number,
      default: Number.MAX_VALUE
    }
  },

  methods: {
    onChange(event) {
      let { files } = event.target;
      if (this.disabled || !files.length) {
        return;
      }

      files = files.length === 1 ? files[0] : [].slice.call(files, 0);
      if (!files || (this.beforeRead && !this.beforeRead(files))) {
        return;
      }

      if (Array.isArray(files)) {
        Promise.all(files.map(this.readFile)).then(contents => {
          let oversize = false;
          const payload = files.map((file, index) => {
            if (file.size > this.maxSize) {
              oversize = true;
            }

            return {
              file: files[index],
              content: contents[index]
            };
          });

          this.onAfterRead(payload, oversize);
        });
      } else {
        this.readFile(files).then(content => {
          this.onAfterRead(
            { file: files, content },
            files.size > this.maxSize
          );
        });
      }
    },

    readFile(file) {
      return new Promise(resolve => {
        const reader = new FileReader();

        reader.onload = event => {
          resolve(event.target.result);
        };

        if (this.resultType === 'dataUrl') {
          reader.readAsDataURL(file);
        } else if (this.resultType === 'text') {
          reader.readAsText(file);
        }
      });
    },

    onAfterRead(files, oversize) {
      if (oversize) {
        this.$emit('oversize', files);
      } else {
        this.afterRead && this.afterRead(files);
        this.$refs.input && (this.$refs.input.value = '');
      }
    }
  },

  render(h) {
    const {
      accept,
      disabled
    } = this;

    return (
      <div class={bem()}>
        {this.slots()}
        <input
          { ...{ attrs: this.$attrs } }
          ref="input"
          type="file"
          accept={accept}
          class={bem('input')}
          disabled={disabled}
          onChange={this.onChange}
        />
      </div>
    );
  }
});