writing Svelte Themes

Writing

My writings published in different sites and aggregated here.

#svelte#sveltejs
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writing

My writings published in different sites and aggregated here.

Quickstart

  • npm install.
  • npm start.

Notes

Svelte

Source: Svelte course by Rich Harris and Frontend Masters.

  • Svelte is a component framework.
  • Svelte is a compiler that takes declarative code and turns it into imperative JS.
  • HTML is the base language rather than JavaScript.
  • Svelte gives a warning if an image (<img>) does not have the alt attribute by default, for example. In other words, Svelte provides accessibility warnings.
  • Styles (<style>) are scoped to the component (and the markup defined in it, not affecting nested components). You can use :global() for global styles.
  • Unused CSS classes are removed from output by default.
  • Use the {@html ...} tag to render strings with HTML. However, Svelte does not perform any sanitization.
  • Svelte + Reactivity:
    • Use $: ($: doubled = count * 2;, for example) for reactive declarations.
    • $: console.log(count);.
    • Svelte’s reactivity is triggered by assignments. So, array methods like push and splice won’t (automatically) cause updates.
  • Use export let variableName; to declare properties/props.
  • Use <Component {...obj}/> to spread props.
  • Keyed each blocks: {#each things as thing (thing.id)}...{/each} ((thing.id) is a unique identifier).
  • Await blocks: {#await promise}...{:then number}...{:catch error}...{/await}.
  • Use Chrome DevTools > Network tab > Online -> Offline (Throttling dropdown) to test catch the error.
  • You can add event modifiers to event handlers (after the on: directive). The once modifier is an example.
  • Components can also dispatch events (component events + event forwarding). In a nutshell, an inner component creates an event (called message, for example), broadcasts it, and then the outer component is able to handle it (on:message={handleMessage}, for example).
  • To leverage event forwarding, add on:click to the button of an inner component to handle it in the App.Svelte file, for example.
  • Bindings (some simple examples):
    • <input bind:value={variableName}>.
    • <input type=checkbox bind:checked={variableName}>.
  • There are bindings for <audio> and <video> as well.
  • Every block-level element has clientWidth, clientHeight, offsetWidth, and offsetHeight bindings (imagine adding this to a <div> with a <span> to know the dimensions of a piece of text).
  • The this binding allows you to obtain a reference to rendered elements.
  • Components (props) can also have bindings.
  • onMount lifecycle function. It runs after the component is first rendered to the DOM.
  • It is possible to have an {:else} in an Each block to render something when the size of the array in question is zero, for example.
  • It is recommended to put the fetch in onMount because of SSR (with the exception of onDestroy, lifecycle functions don’t run during SSR).
  • beforeUpdate and afterUpdate are useful for implementing auto scrolling.
  • When you update component state, it doesn’t update the DOM immediately. Instead, it waits until the next microtask to see if there are any other changes that need to be applied. The tick lifecycle function returns a promise that resolves as soon as any pending state changes have been applied to the DOM.
  • It is possible to reference a store value by prefixing the store name with $ (auto-subscription).
  • It is possible to bind to store values.
  • Svelte provides two motion-oriented functions (tweened and spring) for creating stores whose values change over time rather than immediately. Svelte also provides easing functions.
  • Svelte provides transitions via the transition: directive (or the in: and out: directives) and the functions (e.g., fade) of the svelte/transition module. There are also transition events that can be listened to.
  • Deferred transitions. The crossfade function returns a pair of transitions that talk to each other.
  • Actions are element-level lifecycle functions.
  • Component composition allows a component to accept children. The (default or named) <slot> element is used to specify where these should be placed.
  • The Context API is a mechanism that allows components to talk to each other without data being passed around as props.
  • The <svelte:component> special element is useful for dynamic components.
  • The <svelte:window> special element lets you add event listeners to the window object. It also supports bindings.
  • The <svelte:body> special element lets you add event listeners to the document.body object. It is useful for the mouseenter and mouseleave events, for example.
  • The <svelte:head> special element allows you to insert elements inside the <head>.
  • The <svelte:options> special element allows you to specify compiler options.
  • The <script context=”module”> block will run once, when the module first evaluates, rather than when a component is instantiated.
  • {@debug variableName} for debugging.
  • Svelte Preprocess package.
  • Sapper is an application framework, similar to Next.js (vs. React).
  • Svelte for VS Code:
    • Run Svelte: Restart Language Server if Prettier configuration changes.

UI Kits

Deployment

  • With this configuration, in Vercel, change the OUTPUT DIRECTORY to build (assuming the FRAMEWORK PRESET is Svelte).

Snowpack

Prettier

Accessibility

CSS

Source: CSS for JavaScript Developers course by Josh Comeau.

  • The em unit is a relative unit. It is equal to the font size of the current element.
  • Using em means that a component will change depending on the font size of the container it is placed within.
  • The rem unit is similar to the em unit. However, it is relative to the root element (<html> tag). The author suggests using this unit for font sizes/typography.
  • If necessary, change the baseline font size using em or rem, not px (e.g., html { font-size: 1.2em; }).
  • As for box model properties (padding, border, and margin), the author typically uses px.

Windi CSS

  • Utility-first CSS framework. Alternative to Tailwind CSS.

Misc

References

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