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The fetchFile function is a wrapper around fetch which provides support for path prefixes and some additional loading capabilities.


Use the fetchFile function as follows:

import {fetchFile} from '';

const response = await fetchFile(url);
// or supply any standard `RequestInit` options expected by `fetch`
const response = await fetchFile(url, {headers: {}});

// Now use standard browser Response APIs

// Note: headers are case-insensitive
const contentLength = response.headers.get('content-length');
const mimeType = response.headers.get('content-type');

const arrayBuffer = await response.arrayBuffer();

The Response object from fetchFile is usually passed to parse as follows:

import {fetchFile, parse} from '';
import {OBJLoader} from '';

const data = await parse(fetchFile(url), OBJLoader);

Note that if you don't need the extra features in fetchFile, you can just use the browsers built-in fetch method.

import {parse} from '';
import {OBJLoader} from '';

const data = await parse(fetch(url), OBJLoader);


fetchFile(url: string | Blob, options?: RequestInit) : Promise<Response>

A wrapper around the platform fetch function with some additions:

  • Supports setPathPrefix: If path prefix has been set, it will be appended if url is relative (e.g. does not start with a /).
  • Supports File and Blob objects on the browser (and returns "mock" fetch response objects).


  • A promise that resolves into a fetch Response object, with the following methods/fields:
    • headers: Headers - A Headers object.
    • arrayBuffer(): Promise.ArrayBuffer- Loads the file as anArrayBuffer`.
    • text(): Promise.String` - Loads the file and decodes it into text.
    • json(): Promise.String` - Loads the file and decodes it into JSON.
    • body : ReadableStream` - A stream that can be used to incrementally read the contents of the file.


  • For string URLs - fetchFile will delegate to fetch after resolving the URL.
  • For File/Blob - a Response object will be returned. Any RequestInit options are ignored in this case.
  • Under Node.js, fetchFile (and fetch) works and returns a polyfilled Response object if has been installed, and RequestInit options are used.
  • Response.headers (Content-Length and Content-Type) are populated (on a best effort basis for File, Blob and under Node.js).
  • Use of fetchFile is completely optional. can be used with data loaded via any mechanism the application prefers, e.g. directly using fetch, XMLHttpRequest etc.
  • The setPathPrefix() mechanism is intended to help test cases to load data from the right place, but is not intended to support general application use cases, so use with care.