@h7/compute-js-formdata
v0.1.0
Published
FormData parser and Request.prototype.formData() polyfill for JavaScript. A formal version is coming in the JS runtime, but this can be used in the interim.
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FormData parsing for Fastly Compute JavaScript
by Katsuyuki Omuro
Parses body streams of type multitype/form-data
and provides them as a
polyfill for Request.prototype.formData()
and Response.prototype.formData()
.
This is meant to be used with Fastly Compute, but can probably be used with
any platform that happens to provide Request
/Response
but not
.prototype.formData()
.
Eventually, we expect to see native implementations to be coming to the Fastly Compute JavaScript runtime, and they will be more performant, but this polyfill can be used in the meantime.
Prerequisites
This polyfill does depend on the data structures File
and FormData
, which
at the current time will themselves also need polyfills. blob-polyfill
and
formdata-polyfill
seem to work.
You may face a gotcha when doing this; see the Caveats section below.
Usage
In your Compute project:
npm install blob-polyfill formdata-polyfill @h7/compute-js-formdata
Then, at the beginning of your program:
Object.assign(globalThis, require('blob-polyfill'));
require('formdata-polyfill');
require('@h7/compute-js-formdata');
Now, you can use formData()
:
const req = event.request;
const formData = await req.formData();
formData.get('foo'); // Value of form field 'foo'
Caveats
blob-polyfill
blob-polyfill
does not automatically make its exports available globally, so
you'll have to be sure to copy its exported members such as Blob
and File
to
globalThis
so that they are available to the other polyfills and to your program.
You can do this like this:
// require and merge with globalThis
Object.assign(globalThis, require('blob-polyfill'));
// require other polyfills
require('formdata-polyfill');
require('@h7/compute-js-formdata');
If you're using ES modules (i.e., import
rather than require()
) you'll have
to be extra careful, because import
statements get hoisted.
You'll want to place your blob-polyfill
import in a separate file, e.g.:
// load-blob-polyfill.js
import * as blobPolyfill from 'blob-polyfill';
Object.assign(globalThis, blobPolyfill);
And then import that before the FormData polyfill:
// load blob polyfill and make global
import './load-blob-polyfill.js'
// load other polyfills
require('formdata-polyfill');
require('@h7/compute-js-formdata');
License
MIT.