fetchFile

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

Usage

Use the fetchFile function as follows:

import {fetchFile} from '@loaders.gl/core';

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 '@loaders.gl/core';
import {OBJLoader} from '@loaders.gl/obj';

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 '@loaders.gl/core';
import {OBJLoader} from '@loaders.gl/obj';

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

Functions

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).

Returns:

• 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.

Remarks

• 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 @loaders.gl/polyfills 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. loaders.gl 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.