Svelte Inject

Svelte action to inject elements into the DOM

• Installation
• Why
• Usage

Installation

yarn add -D @mibu/svelte-inject

<script>
	import {inject} from "@mibu/svelte-inject"
</script>

Why

Useful when injectig Svelte into exising code at runtime, e.g. GreaseMonkey userscripts.

You can already inject Svelte components, but only with one injection point per component:

new App({
	target: ..., // Insert into target
	anchor: ... // Insert before child of target
});

Consider modifying a webiste by adding a toggle to the navbar and some toggleable content to an existing content container:

<nav id="navbar">
  <button id="toggle"/> <!-- toggle we want to inject -->
</nav>
<div id="container">
  <div id="content"/> <!-- content we want to inject -->
</div>

You would have to create a component for each and then inject them:

new Toggle({target: document.getElementById("navbar")});
new Content({target: document.getElementById("container")});

But now you are outside the domain of the Svelte compiler and its harder to add reactivity. Lets instead create a App.svelte component and use the inject action:

<script>
	import inject from "@mibu/svelte-inject"
	let showContent = false;
</script>

<button use:inject={"#navbar"} on:click={() => showContent = !showContent}/>
<div use:inject={"#container"} class:hidden={showContent}/>

Now everything is inside one Svelte component and its also reactive.

Usage

The inject action takes one argument {<mode>: <target>}:

• <mode>: Where the element will be injected
• <target>: Either an HTMLElement or a query selector string

<!-- Inject after target -->
<div use:inject={{after: document.getElementById("example")}}>
	...
</div>

<!-- Inject before target -->
<div use:inject={{before: "#example"}}>
	...
</div>

<!-- Append to target -->
<div use:inject={{append: "li.example"}}>
	...
</div>

When you pass just the HTMLElement or a query string, the element will be appended:

<!-- Append to target -->
<div use:inject={document.getElementById("example")}>
	...
</div>

<!-- Append to target -->
<div use:inject={"button.active"}>
	...
</div>

If you don't pass any arguments, the element will be appended to the body:

<!-- Append to document.body -->
<div use:inject>
	...
</div>