Wretch middlewares

A collection of middlewares for the Wretch library.

Installation

$3

Npm

``sh
npm i wretch-middlewares
`

Cdn

`html


`

Middlewares

| Dedupe | Retry | Throttling cache | Delay |
|-----|-----|-----|-----|

Dedupe

Prevents having multiple identical requests on the fly at the same time.

#### Options

- skip : (url, opts) => boolean

If skip returns true, then the dedupe check is skipped.

- key : (url, opts) => string

Returns a key that is used to identify the request.

- resolver : (response: Response) => Response

This function is called when resolving the fetch response from duplicate calls.
By default it clones the response to allow reading the body from multiple sources.

#### Usage

`js
import wretch from 'wretch'
import { dedupe } from 'wretch-middlewares'

wretch().middlewares([
dedupe({
/ Options - defaults below /
skip: (url, opts) => opts.skipDedupe || opts.method !== 'GET',
key: (url, opts) => opts.method + '@' + url,
resolver: response => response.clone()
})
])./ ... /
`

Retry

Retries a request multiple times in case of an error (or until a custom condition is true).

#### Options

- delayTimer : milliseconds

The timer between each attempt.

- delayRamp : (delay, nbOfAttempts) => milliseconds

The custom function that is used to calculate the actual delay based on the the timer & the number of attemps.

- maxAttempts : number

The maximum number of retries before resolving the promise with the last error. Specifying 0 means infinite retries.

- until : (fetchResponse, error) => boolean | Promise

The request will be retried until that condition is satisfied.

- onRetry : ({ response, error, url, options }) => { url?, options? } || Promise<{url?, options?}>

Callback that will get executed before retrying the request. If this function returns an object having url and/or options properties, they will override existing values in the retried request. If it returns a Promise, it will be awaited before retrying the request.

- retryOnNetworkError : boolean

If true, will retry the request if a network error was thrown. Will also provide an 'error' argument to the onRetry and until methods.

- resolver : (response: Response) => Response

This function is called when resolving the fetch response from duplicate calls.
By default it clones the response to allow reading the body from multiple sources.

#### Usage

`js
import wretch from 'wretch'
import { retry } from 'wretch-middlewares'

wretch().middlewares([
retry({
/ Options - defaults below /
delayTimer: 500,
delayRamp: (delay, nbOfAttempts) => delay * nbOfAttempts,
maxAttempts: 10,
until: (response, error) => response && response.ok,
onRetry: null,
retryOnNetworkError: false,
resolver: response => response.clone()
})
])./ ... /

// You can also return a Promise, which is useful if you want to inspect the body:
wretch().middlewares([
retry({
until: response =>
response.json().then(body =>
body.field === 'something'
)
})
])
`

Throttling cache

A throttling cache which stores and serves server responses for a certain amount of time.

#### Options

- throttle : milliseconds

The response will be stored for this amount of time before being deleted from the cache.

- skip : (url, opts) => boolean

If skip returns true, then the dedupe check is skipped.

- key : (url, opts) => string

Returns a key that is used to identify the request.

- clear (url, opts) => boolean

Clears the cache if true.

- invalidate (url, opts) => string | RegExp | Array | null

Removes url(s) matching the string or RegExp from the cache. Can use an array to invalidate multiple values.

- condition response => boolean

If false then the response will not be added to the cache.

- flagResponseOnCacheHit string

If set, a Response returned from the cache whill be flagged with a property name equal to this option.

#### Usage

`js
import wretch from 'wretch'
import { throttlingCache } from 'wretch-middlewares'

wretch().middlewares([
throttlingCache({
/ Options - defaults below /
throttle: 1000,
skip: (url, opts) => opts.skipCache || opts.method !== 'GET',
key: (url, opts) => opts.method + '@' + url,
clear: (url, opts) => false,
invalidate: (url, opts) => null,
condition: response => response.ok,
flagResponseOnCacheHit: '__cached'
})
])./ ... /
`

Delay

Delays the request by a specific amount of time.

#### Options

- time : milliseconds

The request will be delayed by that amount of time.

#### Usage

`js
import wretch from 'wretch'
import { delay } from 'wretch-middlewares'

wretch().middlewares([
delay(1000)
])./ ... /
``