svesta

svesta - is a tiny svelte state management library for svelte/sveltekit.

Installation

# In your project directory
npm install svesta

or

# In your project directory
yarn add svesta

There are 6 major exported components in svesta, they are:

Let us examine each component in detail.

1. Transport

Transport is useful in requesting any arbitrary HTTP(S) endpoint. Transport exposes 2 methods, configure and instance:


import { type TransportConfig, Transport } from 'svesta';

const configOptions:TransportConfig = {
    // Log out details or not. Default is false.
    DEBUG: true,
    // Set the base URL. Default is ''.
    BASE_URL: 'https://some-base-url',
    // External fetch implementation could be passed.
    // Default is undefined.
    // Either window.fetch or fetch from
    // +page.[t|j]s' onload as shown in our example.
    fetch: window.fetch,
    // Allow or disallow migration to web socket.
    // Default is false.
    realTime: false,
    // Allows the override of the base fetch RequestInit.
    // Default is undefined.
    init: RequestInit,
	// If you do not want the transport to be a top-level(default)
	// one, tag it with a context
	// This allows you have multiple transport instances.
	context: 'news', // This is used in accessing the instance later

};

Transport.configure(configOptions);

Best practices favors doing all your Transport configuration in the +layout.[t|j]s in a manageable way. While Transport.configure could be done within your view’s $effect or in your +page.[j|t]s, the recommended place to do the setupu is the +layout.[j|t]s like below:

In +layout.ts


import { Transport } from "svesta";

// This is configured on the default context
Transport.configure({ BASE_URL: 'https://reqres.in/api' });

export const prerender = true;


import { Transport } from 'svesta';

// Just for news, as configured above
const newsTransport = Transport.instance('news');

In +page.[t|j]s

Transport instance plays well with +page.[t|j]s allowing us to specify what fetch to use.

Default context
// from sveltekit
import { Transport } from 'svesta';
import type { PageLoad } from './$types.js';
import { resultTransformer } from '..';

export const load:PageLoad = async ({ fetch }) => {

	// This is happening on the server and we have a ref to a fetch
	// implementation, let's use it by passing it to the configure
	// method of Transport
	
	//Default transport
	const transport  = Transport.instance({fetch});

	const { error , ...rest } = await transport.get('/users');

	return { ...resultTransformer(rest), error };

};
News context
// from sveltekit
import { Transport } from 'svesta';
import type { PageLoad } from './$types.js';
import { resultTransformer } from '..';

export const load:PageLoad = async ({ fetch }) => {

	// This is happening on the server and we have a ref to a fetch
	// implementation, let's use it by passing it to the configure
	// method of Transport
	

	// Scoped only for news
	// Must have been configured too
	const transport  = Transport.instance({context:'news', fetch});

	const { error , ...rest } = await transport.get('/users');

	return { ...resultTransformer(rest), error };

};

Transport competently handles GET, POST, PUT, PATCH, OPTIONS and DELETE HTTP methods via the exposed methods: .get, .post, .put, .patch, .delete, .options and .upload. An example could look like the following:

// Using the default instance
const { error, data } = await Trasport.instance().post(
	'/users', 
	{ name: 'Name', address: 'Some address' }
);


// Using some context(news) instance
const newsTransport = Transport.instance("news");
const { error, data } = await newsTransport.post(
	'/users', 
	{ name: 'Name', address: 'Some address' }
);

Note that you must have configured the news transport context before using it like so:

Transport.configure({context:'news',....});

Transport also exposes a loading, which actually, is a field indicative of whether an active request is happening.

3. useStore

If the target of requests are RESTful APIs, then the appropriate component from svesta is the useStore. useStore defines 2 parameters:

Note: useStore uses Transport under the hood, therefore, configurations set on Transport.configure also affect useStore.

import { type StoreProps, useStore } from 'svesta';

// Create a store props
const usersProps: StoreProps<User> = {
	// Parameters. Default {}
	params: {},
	// Query order asc, desc or [asc|desc]|<field>
	// e.g "desc|id". Default is 'asc'
	orderAndBy: 'asc',
	// namespace allows you proxy a resource with another name
	// E.g. 'profile' could still be used as 'users' namespace.
	// That is profile is not known to you system but 'users'
	// namespace defaults to ''.
	namespace: '',
	// You can pre-populate a store by passing `initData` 
	// of StoreState<T> type
	// It defaults to {}
	initData: {},
	// includes helps control what fields are returned
	// It is pipe-separated string of resource names.
	// resource name is comma-saparate string of fields
	// E.g. 'users:name, age, gender | accounts: accountId, balance' where
	// users and accounts are resource names and their fields are listed after `:`
	// The above example is for when there are relationship
	// in multiple resources(join).
	// It defaults to ''.
	includes: '',
	// resultTransformer is a StoreResultTransformer type, a function you can pass
	// to intercept and convert the data from your API to what
	// `useStore` understands, the StoreState type.
	// This is important when using the `.sync` method of store
	// to synchronize/fetch data from your APIs.
	// It accepts the raw data from your API and
	// returns the transformed data. See transformer.js above.
	// It defaults to undefined
	resultTransformer: undefined,
	// queryTransformer is a StoreQueryTransformer type, a function you can pass
	// to intercept and convert your query to what your API expects.
	// This is important when using the `.sync` method of store
	// to synchronize/fetch data from your APIs.
	// It accepts the raw query and
	// returns the transformed query for your API.
	// It defaults to undefined
	queryTransformer: undefined,
	//Specifies transport context
	transportContext: undefined
};

// Let's create a users store
const users = useStore(
	// resource name, not path please. Required
	'users',
	// store props. Optional
	usersProps
);

// Of all the store arguments, the `resource name/path` is mandatory
// StoreProps is optional and could be omitted, for instance:
const people = useStore('users');

useStore maintains its internal structure as a StoreState<T>. In our example above, T is User. The structure as as shown below:

type StoreState<T> = {
	// result target
	data: T[];
	// total record count
	recordCount: number;
	// Number of pages for limit per page
	pages?: number;
	// What page number are we on?
	page?: number;
	// Record per page
	limit?: number;
	// Are we processing network?
	loading?: boolean;
	// Are there error based on request
	error?: string | null | undefined;
	// Params that produced result or error
	params?: Params;
	transportContext?:string;
};

The reason for a resultTransformer, is to convert API responses that do not conform to StoreState<T>. Look at the API in our example, that is, regres.in. regres.in API returns its response as:

type IngressType = {
	page: number;
	per_page: number;
	total: number;
	total_pages: numbers;
	data: unknow;
};

However, useStore cannot store data like this, hence, the need to implement a result transformer to convert as below:

export const resultTransformer = <User>(raw: IngressType): StoreResult<User> => {
	// raw is what comes from regres.in
	const { page, per_page: limit, total: recordCount, total_pages: pages, data } = raw;
	// return what conforms to StoreState
	return { page, limit, recordCount, pages, data };
};

useStore exposes result, which is a state object comprising of:


import { useStore } from 'svesta';

const { sync, result: { loading, data, error } } = useStore("users");
$effect(() =>{
	sync();
});

	<header>Users</header>
	{#if loading}
		<p>Loading users...</p>
	{/if}
	{#if !!error}
		<p>Error:{error}</p>
	{/if}
	{#if data }
		{#each users as user}
			<p>Name: {user.first_name} {user.last_name} </p>
		{/each}
	{/if}

useStore exposes the following methods:

import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
// force sync
accounts.sync();
// or with initial data
// initData is of type StoreState<Account>
accounts.sync(initData)
import { useStore, Resource, type StoreResult } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
const onNext = () => accounts.next();
const onPrev = () => accounts.prev();
const onMore = () => accounts.more();

Using Resource(we’ll explain next), we can have the following:


{#snippet resolve({ loading, data, error, page, pages }:StoreResult<Account>)}
	
	{#if data}
		<AccountList users={data} />
		<div class="buttons">

			<button onclick={ handlePrev } disabled={ page === 1 }> 
				Previous page
			</button>
			<button onclick={ handleNext } disabled={ page === pages }> 
				Next page
			</button>
			<button onclick={ onMore } disabled={ page === pages }>
				More(append to view)...
			</button>
			
		</div>
	{/if}

	{#if loading}
		<p class='spinner'>Fetching data...</p>
	{if}
	{#if error}
		<p class='danger'>Error: {error}</p>
	{if}
	
{/snippet}

<Resource store={accounts} {resolve} />

import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
// Fire and forget
accounts.save({accountName:'Account Name', accountNo:1234});

// Fire and inspect
const { error, message, data, status } = await accounts.save({accountName:'Account Name', accountNo:1234});
// Do something with fields

import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
// Fire and forget
accounts.destroy({id:12345678});

// Fire and inspect
const { 
	error, 
	message, 
	data, 
	status 
	} = await accounts.destroy({id:12345678});
// Do something with fields

import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
// Fire and forget
// Seach can be added and customized via `queryTransformer`
accounts.search('google');

import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
$effect(async () => {
    // The following will make a GET request to `/accounts/checking`
    // path using the passed params
    const { data, error} = await accounts.get('/checking',{...});
})
import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
$effect(async () => {
    // The following will make a request to POST `/accounts/checking`
    // path using the passed params
    const { data, error} = await accounts.post('/checking',{...});
})
import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
// Seach for `12345` on the `accountId` field
const targetAccount = await accounts.find(key:'accountId', value:12345);
// Check and use targetAccount
import { useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
// Filters for  `accountName` that equals 'Steve Samson'
 accounts.filter({accountName:'Steve Samson'});
import { type EventHandler, useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
const onAccountUpdate:EventHandler = (account:Account) =>{
    console.log(`${account} was updated!`);
};

// onAccountUpdate will be called when update
// happens on any account in the store
accounts.on('update',onAccountUpdate);

The following methods of store do not make network requests when used but they propagate changes to the view. They are added for the purpose of prototyping without persistence. These methods are:


import { type EventHandler, useStore } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('accounts',...);
// id is required
const account = {accountName:'Account Name', accountNo:2345566, id:new Date().getTime()};
accounts.add(account);
accounts.patch({...account, accountName:'Updated Account Name'});
accounts.remove(account);

3. Resource

As mentioned earlier, Resource, is a svelte component, which helps manage the network requests while using store to manage REST resources. Resource also handles resolution of promises and notify of result during an on-going network request, errors on events of HTTP errors or data availability on success.

Resource accepts 2 props:

See example in demo app.

Resource is just a svelte component used as below:

// svelte file
<script>
import { useStore, type StoreResult } from 'svesta';
import type Account from '...';

const accounts = useStore<Account>('some');

</script>


{#snippet resolve({ data, loading, error, page, pages }:StoreResult<Account>)}

	<AccountList users={data} />

	{#if loading}

		<p>Loading data...</p>

	{/if}

	{#if data}
	<div class="buttons">
		<button onclick={ accounts.prev } disabled={ page === 1}> 		
			Previous page
		</button>
		<button onclick={ accounts.next } disabled={ page === pages}> 
			Next page
		</button>
		<button onclick={ accounts.more } disabled={ page === pages }>
			more(append to view)...
		</button>
	</div>
	{/if}

	{#if error}

		<h4>Oh, error?</h4>
		<p>{error}</p>

	{/if}

{/snippet}

<Resource store={accounts} resolve={resolve} />

4. useEvents

useEvents: This allows components exchange informations in a reliable manner, using events rather than passing props. For instance, see the following:

 import {type UseEvent, useEvents } from "svesta";
 // Here loading is the scope of the created event
 const loadEvent: UseEvent<boolean> = useEvents<boolean>('loading');
 ...
 ...
 function start(){
	loadEvent.data = true;
 }
 function done(){
	loadEvent.data = false;
 }

In another component, we can track and use the created loadEvent like so:

<script>
 import {type UseEvent, useEvents } from "svesta";
 // Here loading is the scope of the created event
 const loader: UseEvent<boolean> = useEvents<boolean>('loading');
</script>
{#if loader.data}
	<p>Loading...</p>
{/if}

5. network

network allows the determination of network states. It exposed a status attribute that helps you do that. For instance, when network.status.online is true => online and false => offline. This can be used both in view and non-view components. For instance, the Offline component was build by using network.

6. Offline

This is a svelte component, which displays its children when network.status.online is false. It helps in monitoring network activities in view components. The usage as as shown below:

import { Offline } from 'svesta';

<Offline>
<p>Content to show when offline.</p>
</Offline>