Friday, July 2, 2021

Petite-Vue – 5kb subset of Vue optimized for progressive enhancement

petite-vue

petite-vue is an alternative distribution of Vue optimized for progressive enhancement. It provides the same template syntax and reactivity mental model with standard Vue. However, it is specifically optimized for "sprinkling" small amount of interactions on an existing HTML page rendered by a server framework.

  • Only ~5.7kb
  • DOM-based, mutates in place
  • Driven by @vue/reactivity

Status

  • This is pretty new. There are probably bugs and there might still be API changes, so use at your own risk.

  • The issue list is intentionally disabled because I have higher priority things to focus on for now and don't want to be distracted. If you found a bug, you'll have to either workaround it or submit a PR to fix it yourself. That said, feel free to use the discussions tab to help each other out.

  • Feature requests are unlikely to be accepted at this time - the scope of this project is intentionally kept to a bare minimum.

Usage

petite-vue can be used without a build step. Simply load it from a CDN:

<script src="https://unpkg.com/petite-vue" defer init></script>

<!-- anywhere on the page -->
<div v-scope="{ count: 0 }">
  
  <button @click="count++">inc</button>
</div>
  • Use v-scope to mark regions on the page that should be controlled by petite-vue.
  • The defer attribute makes the script execute after HTML content is parsed.
  • The init attribute tells petite-vue to automatically query and initialize all elements that have v-scope on the page.

Manual Init

If you don't want the auto init, remove the init attribute and move the scripts to end of <body>:

<script src="https://unpkg.com/petite-vue"></script>
<script>
  PetiteVue.createApp().mount()
</script>

Or, use the ES module build:

<script type="module">
  import { createApp } from 'https://unpkg.com/petite-vue?module'
  createApp().mount()
</script>

Production CDN URLs

The short CDN URL is meant for prototyping. For production usage, use a fully resolved CDN URL to avoid resolving and redirect cost:

  • Global build: https://unpkg.com/petite-vue@0.2.0/dist/petite-vue.iife.js
    • exposes PetiteVue global, supports auto init
  • ESM build: https://unpkg.com/petite-vue@0.2.0/dist/petite-vue.es.js
    • Must be used with <script type="module">

Root Scope

The createApp function accepts a data object that serves as the root scope for all expressions. This can be used to bootstrap simple, one-off apps:

<script type="module">
  import { createApp } from 'https://unpkg.com/petite-vue?module'

  createApp({
    // exposed to all expressions
    count: 0,
    // getters
    get plusOne() {
      return this.count + 1
    },
    // methods
    increment() {
      this.count++
    }
  }).mount()
</script>

<!-- v-scope value can be omitted -->
<div v-scope>
  <p></p>
  <p></p>
  <button @click="increment">increment</button>
</div>

Note v-scope doesn't need to have a value here and simply serves as a hint for petite-vue to process the element.

Explicit Mount Target

You can specify a mount target (selector or element) to limit petite-vue to only that region of the page:

createApp().mount('#only-this-div')

This also means you can have multiple petite-vue apps to control different regions on the same page:

createApp({
  // root scope for app one
}).mount('#app1')

createApp({
  // root scope for app two
}).mount('#app2')

Lifecycle Events

You can listen to the mounted and unmounted lifecycle events for each element:

<div
  v-if="show"
  @mounted="console.log('mounted on: ', $el)"
  @unmounted="console.log('unmounted: ', $el)"
></div>

v-effect

Use v-effect to execute reactive inline statements:

<div v-scope="{ count: 0 }">
  <div v-effect="$el.textContent = count"></div>
  <button @click="count++">++</button>
</div>

The effect uses count which is a reactive data source, so it will re-run whenever count changes.

Components

The concept of "Components" are different in petite-vue, as it is much more bare-bones.

First, reusable scope logic can be created with functions:

<script type="module">
  import { createApp } from 'https://unpkg.com/petite-vue?module'

  function Counter(props) {
    return {
      count: props.initialCount,
      inc() {
        this.count++
      },
      mounted() {
        console.log(`I'm mounted!`)
      }
    }
  }

  createApp({
    Counter
  }).mount()
</script>

<div v-scope="Counter({ initialCount: 1 })" @mounted="mounted">
  <p></p>
  <button @click="inc">increment</button>
</div>

<div v-scope="Counter({ initialCount: 2 })">
  <p></p>
  <button @click="inc">increment</button>
</div>

Components with Template

If you also want to reuse a piece of template, you can provide a special $template key on a scope object. The value can be the template string, or an ID selector to a <template> element:

<script type="module">
  import { createApp } from 'https://unpkg.com/petite-vue?module'

  function Counter(props) {
    return {
      $template: '#counter-template',
      count: props.initialCount,
      inc() {
        this.count++
      }
    }
  }

  createApp({
    Counter
  }).mount()
</script>

<template id="counter-template">
  My count is 
  <button @click="inc">++</button>
</template>

<!-- reuse it -->
<div v-scope="Counter({ initialCount: 1 })"></div>
<div v-scope="Counter({ initialCount: 2 })"></div>

The <template> approach is recommended over inline strings because it is more efficient to clone from a native template element.

Global State Management

You can use the reactive method (re-exported from @vue/reactivity) to create global state singletons:

<script type="module">
  import { createApp, reactive } from 'https://unpkg.com/petite-vue?module'

  const store = reactive({
    count: 0,
    inc() {
      this.count++
    }
  })

  // manipulate it here
  store.inc()

  createApp({
    // share it with app scopes
    store
  }).mount()
</script>

<div v-scope="{ localCount: 0 }">
  <p>Global </p>
  <button @click="store.inc">increment</button>

  <p>Local </p>
  <button @click="localCount++">increment</button>
</div>

Custom Directives

Custom directives are also supported but with a different interface:

const myDirective = (ctx) => {
  // the element the directive is on
  ctx.el
  // the raw value expression
  // e.g. v-my-dir="x" then this would be "x"
  ctx.exp
  // v-my-dir:foo -> "foo"
  ctx.arg
  // v-my-dir.mod -> { mod: true }
  ctx.modifiers
  // evaluate the expression and get its value
  ctx.get()
  // evaluate arbitrary expression in current scope
  ctx.get(`${ctx.exp} + 10`)

  // run reactive effect
  ctx.effect(() => {
    // this will re-run every time the get() value changes
    console.log(ctx.get())
  })

  return () => {
    // cleanup if the element is unmounted
  }
}

// register the directive
createApp().directive('my-dir', myDirective).mount()

This is how v-html is implemented:

const html = ({ el, get, effect }) => {
  effect(() => {
    el.innerHTML = get()
  })
}

Examples

Check out the examples directory.

Features

petite-vue only

  • v-scope
  • v-effect
  • @mounted & @unmounted events

Has Different Behavior

  • Most expressions has access to its bound element as $el (except for structural directives like v-if and v-for)
  • createApp() (accepts global state instead of root component)
  • Components
  • Custom directives

Vue Compatible

  • text bindings
  • v-bind (including : shorthand and class/style special handling)
  • v-on (including @ shorthand and all modifiers)
  • v-model (all input types + non-string :value bindings)
  • v-if / v-else / v-else-if
  • v-for
  • v-show
  • v-html
  • v-text
  • v-pre
  • v-once
  • v-cloak
  • reactive()
  • nextTick()

Not Supported

Some features are dropped because they have a relatively low utility/size ratio in the context of progressive enhancement. If you need these features, you should probably just use standard Vue.

  • ref(), computed() etc.
  • Template refs (just use selectors)
  • Render functions (petite-vue has no virtual DOM)
  • Reactivity for Collection Types (Map, Set, etc., removed for smaller size)
  • Transition, KeepAlive, Teleport, Suspense
  • v-for deep destructure
  • v-on="object"
  • v-is & <component :is="xxx">
  • v-bind:style auto-prefixing

Relationship with Alpine

  • This is indeed addressing a similar scope to Alpine, but aims to be even more minimal.
    • petite-vue is less than half the size of Alpine.
    • petite-vue has no transition system (maybe this can be an opt-in plugin).
  • Alpine is developing its own ecosystem and likely will diverge more from Vue in the future. petite-vue aligns with standard Vue behavior whenever possible, so it's less friction moving to standard Vue if needed. It's intended to cover the progressive enhancement use case where standard Vue is less optimized for nowadays.


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