fetch('<https://api.graph.cool/file/v1/cj3rp40vd64ho0113z6fynxxm>', {
      method: 'POST',
      body: data
    }).then(response => {
      console.log(JSON.stringify(response, null, 2))
      return response.json()
    }).then(file => {
      console.log(file);
    }).catch(err => {
      console.log('err : ', err);
    })

data

const data = new FormData();
    data.append('data', strBase64, 'test.png');