code: function inferResponseType (src) {
    var dotLastIndex = src.lastIndexOf('.');
    if (dotLastIndex >= 0) {
      var extension = src.slice(dotLastIndex, src.length);
      if (extension === '.gltf' || extension === '.glb') {
        return 'arraybuffer';
      }
    }
    return 'text';
  }
docs: Infer response-type attribute from src.
  Default is text(default XMLHttpRequest.responseType)
  but we use arraybuffer for .gltf and .glb files
  because of THREE.GLTFLoader specification.
  
  @param {string} src
  @returns {string}