How does axios handle blob vs arraybuffer as responseType?

When using Axios for network requests, if you need to handle binary data such as images, audio files, or other media resources, you might use blob or arraybuffer as responseType. These types enable you to directly process raw binary data in JavaScript.

Using blob as responseType

When you set responseType to blob, the response data is returned as a Blob object. Blob objects represent immutable, raw data in a file-like format, making them particularly useful for handling image or other file-type data. For example, if you are downloading an image and want to display it on a webpage, you can do the following:

javascript
axios({
  method: 'get',
  url: 'http://example.com/image.png',
  responseType: 'blob'
}).then(function (response) {
  const url = URL.createObjectURL(response.data);
  const img = document.createElement('img');
  img.src = url;
  document.body.appendChild(img);
}).catch(function (error) {
  console.log(error);
});

In this example, we send a GET request to retrieve an image file. Setting responseType to blob ensures the response returns a Blob object. By using URL.createObjectURL(), we convert this Blob object into a URL and assign it to the src attribute of an image element, thereby displaying it on the webpage.

Using arraybuffer as responseType

ArrayBuffer objects represent generic, fixed-length buffers for raw binary data. You can use them to handle audio, video, or other binary data streams. For example, if you need to process an audio file returned from the server and play it using the Web Audio API, you can do the following:

javascript
axios({
  method: 'get',
  url: 'http://example.com/audio.mp3',
  responseType: 'arraybuffer'
}).then(function (response) {
  const audioContext = new AudioContext();
  audioContext.decodeAudioData(response.data, function(buffer) {
    const source = audioContext.createBufferSource();
    source.buffer = buffer;
    source.connect(audioContext.destination);
    source.start(0);
  }, function(e) {
    console.log("Error decoding audio data: " + e.err);
  });
}).catch(function (error) {
  console.log(error);
});

In this example, we set responseType to arraybuffer to obtain the raw audio data. Then, we use AudioContext.decodeAudioData to decode the audio data and play it.

In summary, depending on your specific needs, you can choose between blob or arraybuffer as responseType to handle various types of binary data. Both approaches effectively allow you to directly process files and data streams in JavaScript.