文件处理JS

FileHelper.js

class FileHelper {
  FetchToBlob(url, opt = {}) {
    return new Promise((reslove, reject) => {
      if (!url) {
        reject()
        return
      }
      fetch(url, opt).then(function (response) {
        if (response.ok) {
          reslove(response.blob());
          return
        }
        console.log(response);
        reject(response)
        return
      }).catch(function (error) {
        console.log('There has been a problem with your fetch operation: ', error.message);
        reject(error)
        return
      });
    })
  }

  BlobToDataURL(blob) {
    return new Promise((reslove) => {
      var reader = new FileReader();
      reader.onload = function (e) {
        reslove(e.target.result)
      };
      reader.readAsDataURL(blob);
    })
  }

  // https://gist.github.com/fupslot/5015897
  DataURIToBlob(dataURI) {
    return new Promise((reslove, reject) => {
      if (dataURI && dataURI.indexOf(",")) {
        // base64 => const base64Str = Buffer.from(str, 'utf8').toString('base64');
        // var byteString = atob(dataURI.split(',')[1]);
        const byteString = Buffer.from(dataURI.split(',')[1], 'base64').toString('utf8');

        // separate out the mime component
        var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0]

        // write the bytes of the string to an ArrayBuffer
        var ab = new ArrayBuffer(byteString.length);
        var ia = new Uint8Array(ab);
        for (var i = 0; i < byteString.length; i++) {
          ia[i] = byteString.charCodeAt(i);
        }

        // write the ArrayBuffer to a blob, and you're done
        var bb = new Blob([ab]);
        reslove({
          "blob": bb,
          "mime": mimeString,
        })
      } else {
        reject({})
      }
    })
  }
}

export default new FileHelper()