three.js/examples/jsm/loaders/XLoader.d.ts

import {
  Mesh,
  Loader,
  LoadingManager
} from '../../../src/Three';

export interface XResult {
  animations: object[];
  models: Mesh[];
}

export class XLoader extends Loader {
  constructor(manager?: LoadingManager);

  load(url: string, onLoad: (object: XResult) => void, onProgress?: (event: ProgressEvent) => void, onError?: (event: ErrorEvent) => void): void;
  parse(data: ArrayBuffer | string, onLoad: (object: object) => void): object;
}