A utility that makes reading multipart responses simple
This is free to use software, but if you do like it, consisder supporting me β€οΈ
β‘ Features
- No dependencies
- Seemless api
- Super performant
- Supports any1
content-type
- preamble and epilogue don't yield
- Browser/Node Compatible
- Plugs into existing libraries like Relay and rxjs
π Usage
Visit /examples for more info!
// Relies on bundler/environment detection
import { meros } from 'meros';
const parts = await fetch('/api').then(meros);
// As a simple Async Generator
for await (const part of parts) {
// Do something with this part
}
// Used with rxjs streams
from(parts).subscribe((part) => {
// Do something with it
});
Specific Environment
Browser
import { meros } from 'meros/browser';
// import { meros } from 'https://cdn.skypack.dev/meros';
const parts = await fetch('/api').then(meros);
Node
import http from 'http';
import { meros } from 'meros/node';
const response = await new Promise((resolve) => {
const request = http.get(`http://example.com/api`, (response) => {
resolve(response);
});
request.end();
});
const parts = await meros(response);
π API
Meros offers two flavours, both for the browser and for node; but their api's are fundamentally the same.
Note: The type
Response
is used loosely here and simply alludes to Node'sIncomingMessage
or the browser'sResponse
type.
meros(response: Response, options?: Options)
Returns: Promise<Response | AsyncGenerator<Part | Part[]>>
Meros returns a promise that will resolve to an AsyncGenerator
if the response is of multipart/mixed
mime, or simply
returns the Response
if something else; helpful for middlewares. The idea here being that you run meros as a chain off
fetch.
fetch('/api').then(meros);
If the
content-type
is NOT a multipart, then meros will resolve with the response argument.Example on how to handle this case
import { meros } from 'meros'; const response = await fetch('/api'); // Assume this isnt multipart const parts = await meros(response); if (parts[Symbol.asyncIterator] < 'u') { for await (const part of parts) { // Do something with this part } } else { const data = await parts.json(); }
each Part
gives you access to:
json: boolean
~ Tells you thebody
would be a JavaScript object of your defined genericT
.headers: object
~ A key-value pair of all headers discovered from this part.body: T | Fallback
~ Is the body of the part, either as a JavaScript object (noted byjson
) or the base type of the environment (Buffer | string
, for Node and Browser respectively).
options.multiple: boolean
Default: false
Setting this to true
will yield once for all available parts of a chunk, rather than yielding once per part. This is
an optimization technique for technologies like GraphQL where rather than commit the payload to the store, to be
added-to in the next process-tick we can simply do that synchronously.
Warning: This will alter the behaviour and yield arraysβthan yield payloads.
const chunks = await fetch('/api').then((response) => meros(response, { multiple: true }));
// As a simple Async Generator
for await (const parts of chunks) {
for (const part of parts) {
// Do something with this part, maybe aggregate?
}
}
π¨ Benchmark
via the
/bench
directory with Node v18.0.0
Node
β meros ~ 1,271,218 ops/sec Β± 0.84%
β it-multipart ~ 700,039 ops/sec Β± 0.72%
--
it-multipart (FAILED @ "should match reference patch set")
Browser
β meros ~ 800,941 ops/sec Β± 1.06%
β fetch-multipart-graphql ~ 502,175 ops/sec Β± 0.75%
--
fetch-multipart-graphql (FAILED @ "should match reference patch set")
π Notes
Why the name? meros comes from Ancient Greek ΞΌΞΟΞΏΟ mΓ©ros, meaning "part".
This library aims to implement RFC1341 in its entirety, however we aren't there yet. That being said, you may very well use this library in other scenarios like streaming in file form uploads.
Another goal here is to aide in being the defacto standard transport library to support
@defer
and @stream
GraphQL directives
Caveats
- No support the
/alternative
,/digest
or/parallel
subtype at this time. - No support for nested multiparts
β€ Thanks
Special thanks to Luke Edwards for performance guidance and high level api design.
π Compassion
This library is simple, a mere few hundred bytes. It's easy to copy, and easy to alter. If you do, that is fine β€οΈ I'm all for the freedom of software. But please give credit where credit is due.
License
MIT Β© Marais Rossouw
Footnotes
-
By default, we'll look for JSON, and parse that for you. If not, we'll give you the body as what was streamed. β©