axios

  .get('/captcha', {

    params: param,

    responseType: 'arraybuffer'

  })

  .then(response => {

    return 'data:image/png;base64,' + btoa(

      new Uint8Array(response.data)

        .reduce((data, byte) => data + String.fromCharCode(byte), '')

    );

  }).then(data => {

    ...

  })

 这样写即可，

如果请求中没有额外的头信息，只需要加img标签src=请求接口地址即可