v-lazy-show
v0.2.4
Published
Compile-time directive to lazy initialize v-show for Vue
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v-lazy-show
A compile-time directive to lazy initialize v-show for Vue. It makes components mount after first truthy value (v-if
), and the DOM keep alive when toggling (v-show
).
Install
npm i -D v-lazy-show
This package is completely compile-time, installed it as a nodeTransformer
in Vue's compiler options.
For example in Vite:
// vite.config.ts
import { defineConfig } from 'vite'
import { transformLazyShow } from 'v-lazy-show'
export default defineConfig({
plugins: [
Vue({
template: {
compilerOptions: {
nodeTransforms: [
transformLazyShow, // <--- add this
],
},
},
}),
]
})
In Nuxt:
// nuxt.config.ts
export default defineNuxtConfig({
modules: [
'v-lazy-show/nuxt'
]
})
Usage
You can use it as a directive. Both v-lazy-show
and v-show.lazy
are supported and equivalent.
<script setup lang="ts">
const show = ref(false)
</script>
<template>
<div v-lazy-show="show">
<MyComponent />
</div>
</template>
With it, <MyComponent />
will not be mounted for the first render. Until the first time show.value = true
, it will be mounted and the DOM will be kept alive. Later if you switch show.value
back to false
, <MyComponent />
will not be unmounted, instead, display: none
will be applied to the DOM just like v-show
.
Use Cases
It can be helpful to use with some component that is expensive to create/mount. For example, if you have a tabs component, that some tab contains a heavy component. Using v-if
, it will get the component destroyed and re-created when switching tabs. Using v-show
, you will need to pay the mounting cost on the initial render even you haven't switch to that tab yet.
With v-lazy-show
, you can have the best of both worlds. You can think it as a v-show
that lazy initializes, or a v-if
that caches the DOM.
Similarly, this can be helpful for <details>
, <dialog>
, <tabs>
, <popups>
and other components that you want to keep the DOM alive when toggling.
How does it work?
Like how v-if
works, when you use this directive, it hint the compiler to do some transformation to the generated vnodes.
<template>
<div v-lazy-show="foo">
Hello
</div>
</template>
will be compiled to
import { Fragment as _Fragment, createCommentVNode as _createCommentVNode, createElementBlock as _createElementBlock, createElementVNode as _createElementVNode, openBlock as _openBlock, vShow as _vShow, withDirectives as _withDirectives } from 'vue'
export function render(_ctx, _cache) {
return (_cache._lazyshow1 || _ctx.foo)
? (_cache._lazyshow1 = true, (_openBlock(),
_withDirectives(_createElementVNode('div', null, ' Hello ', 512 /* NEED_PATCH */), [
[_vShow, _ctx.foo]
])))
: _createCommentVNode('v-show-if', true)
}
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License
MIT License © 2022 Anthony Fu