Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/kaisermann/svelte-loadable

Dynamically load a svelte component
https://github.com/kaisermann/svelte-loadable

code-splitting dynamic-import loadable-components svelte

Last synced: 8 days ago
JSON representation

Dynamically load a svelte component

Awesome Lists containing this project

README 

        
# svelte-loadable



> Dynamically load a svelte component. Based on [react-loadable](https://github.com/jamiebuilds/react-loadable).



## Usage



Just pass a `loader` method which return a async module import:



```html



  import Loadable from 'svelte-loadable'



 import('./AsyncComponent.svelte')} />

```



Use `unloader` to prevent `Loadable` from caching the component which will cause it to call `loader` each time the component is used after being unmounted.



```html



  import Loadable from 'svelte-loadable'



  // unloader callback

  function unloader() {

    // some code here

  }



 { /* some code here */ }} />



 System.import('./AsyncComponent.svelte')} unloader={()

=> System.delete(System.resolve('./AsyncComponent.svelte'))} />

```



### Props



- `loader`: a function which `import()` your component to the `` component.

- `delay`: minimum delay in `msecs` for showing the `loading slot`. Default: 200

- `timeout`: time in `msecs` for showing the `timeout slot`.

- `unloader`: `true` to prevent the component from being cached or a `function` which will also prevent the component from being cached after being unmounted and will be called immediately after it is removed from cache.



Any other prop will be passed directly onto the rendered component if the `default` slot is defined:



```html



```



If the default slot is used, it's up to the developer to render the component:



```html



  



```



### Events



- `on:load`: a function which is executed right after the `` component is loaded.



```html

 console.log('The component has been loaded')}

loader={...} />

```



Otherwise, if your callback contains more code, you can wrap it into a function, and call it without parentheses



```html



```



### Slots



- `loading`: customizes the loading state;

- `error`: customizes the error state. You can `let:error` to have access to the error variable, and `let:retry` to have access to the retry method.

- `timeout`: customizes the timeout state. Will only appear if `timeout` prop is defined;

- `default`: customizes the imported component render (add props, etc). You can `let:component` to access the imported component constructor.



#### Basic Example



```html



  import Loadable from 'svelte-loadable'



 import('./AsyncComponent.svelte')}>

  
Loading...


  


    {error}

    


    Try again

  



```



### Registering a loader



#### Or, preventing "flash of loading"



By default, Svelte Loadable will dynamically load the specified loader (import statement) every time the component is initialized and reinitialized. This creates a delay between initial rendering, and rending the loaded component, even for components which have previously been loaded. To work around that, Svelte Loadable provides an optional cache, which can be used to predefine a loader, and keep track of whether it has already been loaded. When a loader is registered, it will render immediately on the next initialization.



To set that up, you'll need to `register` the loader at definition time in a module script block, instead of passing the loader directly to the loadable component instance, then pass the resulting loader on to the loadable component. It looks like this (with `svelte-routing`).



_NOTE:_ A resolve function is necessary for most SSR solutions. The function must return an absolute path, which will be used for indexing, and for loading before hydration. The specific way to generate that may vary by platform. A babel plugin for Svelte Loadable to help generate that automatically is forthcoming.



**App.svelte:**



```html



  import { register } from 'svelte-loadable'



  // Loaders must be registered outside of the render tree.

  const PageLoader = register({

    loader: () => import('./pages/Page.svelte'),

    resolve: () => require.resolve('./pages/Page.svelte'),

  })

  const HomeLoader = register({

    loader: () => import('./home/Home.svelte'),

    resolve: () => require.resolve('./home/Home.svelte'),

  })



  import { Router, Link, Route } from 'svelte-routing'

  import Loadable from 'svelte-loadable'



  export let url = ''



  

    

      
Loading...


    

  

  

    

  



```



Another advantage is that if the same module is registered in two different places in the tree, the previous loader will be used instead of creating a second loader.



This comes with additional benefits and opportunities as well. There is now a `preloadAll` method, which can be used to proactively (and recursively) preload all the modules after the initial render of the application, if desired. That method can also be used server side to preload all the necessary components to pull off server side rendering (SSR).



### Additional Methods



#### preloadAll()



Preloads all registered Loaders. Works server side, and client side.



```js

import { preloadAll } from 'svelte-loadable'



// Somewhere in your code, after the initial tree is rendered:

preloadAll().then(() => {...});

```



### The 'svelte-loadable-capture' Context for SSR



To facilitate the creation of SSR solutions, Svelte Loadable uses a context which can be set up by an SSR solution in a `LoadableProvider` using the string identifier 'svelte-loadable-capture'. Svelte Loadable expects the context to provide a method, to which it will pass the registered loader function. For an example implementation, check out [`npdev:svelte-loadable`](https://github.com/CaptainN/npdev-svelte-loadable) a Meteor SSR solution.



---



For more examples, please check the [`example/src/App.svelte`](https://github.com/kaisermann/svelte-loadable/blob/master/example/src/App.svelte) file.