Action Parameters and Updates
Pass parameters to actions and react to parameter changes with the update method.
Action Parameters and Updates is a free Sveltejs Academy lesson on CoddyKit. This is lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Sveltejs Academy learning path, and your progress syncs across the web and the CoddyKit app. The Sveltejs Academy course includes 4 lessons in total.
Parameterized Actions
Actions can accept a second argument: parameters from the consumer.
function tooltip(node, text) {
// ...
}Apply with Parameters
Pass the value with curly braces after the colon.
<button use:tooltip={"Save document"}>Save</button>Reactive Parameters
If parameters change, the action's update method runs.
return {
update(newText) { /* react to change */ },
destroy() { /* cleanup */ }
};Return Object
An action can return an object with update and destroy for full lifecycle control.
Pattern Example
A tooltip action whose text updates reactively as the user types in a field.
Complex Params
Pass objects for multiple options.
<div use:popper={{ placement: "top", offset: 8 }}>Default Parameters
Handle undefined gracefully inside the action.
function tip(node, params = {}) { ... }TypeScript Types
Type the parameter shape with the Action generic for safe consumer use.
Stable Identity
Avoid passing inline objects that change every render; they may force unnecessary updates.
Order of Lifecycle
Action runs on mount; update runs when params change; destroy runs on unmount.
Avoid Heavy Updates
Keep update logic efficient — it may run many times.
Quick Check
How do you react to parameter changes inside an action?
Recap
Actions accept parameters and can return update/destroy handlers to react to changes and clean up.
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Frequently Asked Questions
Is the “Action Parameters and Updates” lesson free?
Yes — the full text of “Action Parameters and Updates” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Sveltejs Academy course, upgrade to CoddyKit PRO. The Sveltejs Academy course includes 4 lessons in total.
What will I learn in “Action Parameters and Updates”?
Pass parameters to actions and react to parameter changes with the update method. You practise Sveltejs Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Sveltejs Academy?
No prior experience is required. Sveltejs Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.
How long does the “Action Parameters and Updates” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Sveltejs Academy lesson?
Yes. Every Sveltejs Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- use: Directive Syntax
- Action Parameters and Updates
- The destroy() Cleanup Function
- Practical Actions: clickOutside tooltip autofocus