micro-ftch
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Wrappers for built-in fetch() enabling killswitch, logging, concurrency limit and other features
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# micro-ftch
Wrappers for [built-in fetch()](https://developer.mozilla.org/en-US/docs/Web/API/fetch) enabling killswitch, logging, concurrency limit and other features.
fetch is great, however, its usage in secure environments is complicated. The library makes it simple.
## Usage
A standalone file
[micro-ftch.js](https://github.com/paulmillr/micro-ftch/releases) is also available.
> `npm install micro-ftch`
> `jsr add jsr:@paulmillr/micro-ftch`
```ts
import { ftch, jsonrpc, replayable } from 'micro-ftch';
let enabled = false;
const net = ftch(fetch, {
isValidRequest: () => enabled,
log: (url, options) => console.log(url, options),
timeout: 5000,
concurrencyLimit: 10,
});
const res = await net('https://example.com');
// Composable
const rpc = jsonrpc(net, 'http://rpc_node/', {
headers: {},
batchSize: 20,
});
const res1 = await rpc.call('method', 'arg0', 'arg1');
const res2 = await rpc.callNamed('method', { arg0: '0', arg1: '1' }); // named arguments
const testRpc = replayable(rpc);
// Basic auth auto-parsing
await net('https://user:pwd@httpbin.org/basic-auth/user/pwd');
```
- [ftch](#ftch)
- [isValidRequest](#isValidRequest)
- [log](#log)
- [timeout](#timeout)
- [concurrencyLimit](#concurrencyLimit)
- [Basic auth](#basic-auth)
- [jsonrpc](#jsonrpc)
- [replayable](#replayable)
- [Privacy](#privacy)
- [License](#license)
There are three wrappers over `fetch()`:
1. `ftch(fetch)` - isValidRequest, logging, timeouts, concurrency limits, basic auth
2. `jsonrpc(fetch)` - batched JSON-RPC functionality
3. `replayable(fetch)` - log & replay network requests without actually calling network code.
## ftch
Basic wrapper over `fetch()`.
### isValidRequest
When isValidRequest killswitch is enabled, all requests will throw an error.
You can dynamically enable and disable it any any time.
```ts
let ENABLED = true;
const f = ftch(fetch, { isValidRequest: () => ENABLED });
f('http://localhost'); // ok
ENABLED = false;
f('http://localhost'); // throws
ENABLED = true;
f('http://localhost'); // ok
```
### log
```ts
const f = ftch(fetch, { log: (url, opts) => console.log('fetching', url, opts) });
f('http://url/'); // will print request information
```
### timeout
```ts
// browser and OS may have additional timeouts, we cannot override them
// a: per-request timeout
const f = ftch(fetch);
const res = await f('http://url/', { timeout: 1000 }); // throws if request takes more than one second
// b: timeout for all
const f = ftch(fetch, { timeout: 1000 });
const res = await f('http://url/'); // throws if request takes more than one second
```
### concurrencyLimit
Allows to not accidentally hit rate limits or do DoS.
```ts
// browser and OS may have additional limits, we cannot override them
const f = ftch(fetch, { concurrencyLimit: 1 });
const res = await Promise.all([f('http://url1/'), f('http://url2/')]); // these would be processed sequentially
```
### Basic auth
```ts
const f = ftch(fetch);
const res = await f('https://user:pwd@httpbin.org/basic-auth/user/pwd'); // supports basic auth!
```
### jsonrpc
Supports batching multiple HTTP requests into one "Batched" JSON RPC HTTP request. Can massively speed-up when servers are single-threaded, has small per-user limits
```ts
const rpc = jsonrpc(fetch, 'http://rpc_node/', {
headers: {},
batchSize: 20,
});
const res = await rpc.call('method', 'arg0', 'arg1');
const res2 = await rpc.callNamed('method', { arg0: '0', arg1: '1' }); // named arguments
```
### replayable
Small utility to log & replay network requests in tests, without actually calling network code.
```ts
const ftch = ftch(fetch);
const replayCapture = replayable(ftch); // wraps fetch
await replayCapture('http://url/1'); // real network
await replayCapture('http://url/2');
const logs = replayCapture.export(); // Exports logs
// When logs provided - use cached version (faster)
const replayTest = replayable(ftch, JSON.parse(logs));
await replayTest('http://url/1'); // cached
await replayTest('http://url/2'); // cached
await replayTest('http://url/3'); // real network
// When done and everything is captured, turn on 'offline' mode to throw on network requests:
const replayTestOffline = replayable(ftch, JSON.parse(logs), {
offline: true,
});
await replayTest('http://url/1'); // cached
await replayTest('http://url/2'); // cached
await replayTest('http://url/3'); // throws!
```
## Privacy
ftch() disables referrer by default by setting `referrerPolicy: 'no-referrer'`.
## License
MIT (c) Paul Miller [(https://paulmillr.com)](https://paulmillr.com), see LICENSE file.