Svelte Invalidable store

A Svelte that can be requested to update itself

Installation

npm install @macfja/svelte-invalidable

Goal

The idea behind this store is to provide a way to make a store to refresh it's base on an external event.

For example your store contains data that are dependent on an external API. Instead of creating a logic outside your store to update it, this store to just say "your data is not up-to-date, go get the new data"

Usage

import { invalidable } from "@macfja/svelte-invalidable"
import { writable } from "svelte/store"

let name = invalidable(writable("John"), () => {
    // your custom logic here
    return "the new value that you compute just before"
})

name.invalidate()

import { pinvalidable } from "@macfja/svelte-invalidable"
import { writable } from "svelte/store"

let name = pinvalidable(writable("John"), () => {
    // your custom logic here
    // your should return a Promise (for example from a fetch)
    // The store will only be updated when the promise is revolved
    return new Promise(resolve => {resolve("Doe")})
})

name.invalidate()

Example

<script>
    import { invalidate, invalidable, pinvalidable } from "@macfja/svelte-invalidable"
    import { writable } from "svelte/store"

    let time = pinvalidable(writable("Never"), () => {
        return fetch("https://worldtimeapi.org/api/timezone/Etc/UTC")
            .then(r => r.json())
            .then(r => r.datetime)
    })

    const updateTime = () => {
        time.invalidate()
    }

    const updating = time.isUpdating
    const values = [2, 7, 3, 5, 11, 13]
    let position = 0
    let data = invalidable(writable(2), () => values[(++position)%6])
</script>

<p>The last time the date was refresh is: {$time} {#if $updating}(Updating...){/if}</p>
<button id="date-btn" on:click={updateTime}>Do it now</button>

<hr />
<var on:click={() => invalidate(data)}>prime number: {$data}</var>

(REPL)

<script>
    import {pinvalidable} from "@macfja/svelte-invalidable"
    import { writable, derived } from "svelte/store"

    let quantity = 1
    let price = pinvalidable(writable(10), () => {
        // Simulate long calculation + network access
        return new Promise(r => setTimeout(() => r(Math.round(quantity * 10 * 0.8)), 1000))
    })
    let discount = derived([price], ([finalPrice]) => {
        return (10 * quantity) - finalPrice
    })
    const increase = () => {
        quantity++
        $price = quantity * 10
        // Indicate that the price should be recalculated
        price.invalidate()
    }
</script>
<h2>Shopping cart</h2>
<ul>
    <li>
        <ul>
            <li>Product #1553879</li>
            <li>Unit Price: 10¤</li>
            <li>Quantity {quantity} <button id="increase-qty" on:click={increase}>+</button></li>
        </ul>
    </li>
</ul>
<dl>
    <dt>Subtotal</dt>
    <dd id="subtotal">{10 * quantity}¤</dd>
    <dt>Total</dt>
    <dd id="total">{$price}¤ ({$discount}¤ of discount)</dd>
</dl>

(REPL)

Contributing

Contributions are welcome. Please open up an issue or create PR if you would like to help out.

Read more in the Contributing file

License

The MIT License (MIT). Please see License File for more information.