How to Work with Props in Svelte: A Guide for Developers

In this article, we will explore how to effectively work with props in Svelte, allowing components with a parent/child relationship to communicate with each other. By understanding how to pass data through props, you can create dynamic and interactive components in your Svelte applications.

To start, let’s take a look at how to import a Svelte component into another component. You can achieve this by using the following syntax:

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<script>
import SignupForm from './SignupForm.svelte';
</script>

Here, the path specified in the import statement should be relative to the current component’s path. For example, using ./ refers to the current folder, while using ../ would indicate going back one folder.

Once you have imported the component, you can use it in your markup as if it were an HTML tag:

1	<SignupForm />

By including the imported component in this way, you establish a parent/child relationship between the two components, with the importing component acting as the parent and the imported component as the child.

Now, let’s discuss how to pass data from the parent component to the child component using props. Props in Svelte behave similarly to attributes in plain HTML and allow for one-way communication.

To pass a prop, you specify it in the markup by using the appropriate syntax. For example, you can pass a prop named disabled with a value of true like this:

1	<SignupForm disabled={true}/>

In the child component, you need to explicitly define and export the prop using the export keyword in the component script:

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<script>
 export let disabled
</script>

This step is crucial in indicating that the prop is exposed to parent components and can be used for communication.

Additionally, props can accept dynamic values by passing variables instead of static values. This allows you to update the prop value dynamically. Here’s an example of how to pass a variable named disabled as the prop:

<script>
import SignupForm from './SignupForm.svelte';
let disabled = true
</script>

<SignupForm disabled={disabled}/>

With this setup, whenever the value of the disabled variable changes, the change will be propagated to the child component through the prop.

To demonstrate, consider the following scenario. Let’s say you initially set the disabled variable to true, but after a delay of 2000 milliseconds, you update it to false:

<script>
import SignupForm from './SignupForm.svelte';
let disabled = true
setTimeout(() => { disabled = false }, 2000)
</script>

<SignupForm disabled={disabled}/>

During this time, the child component will receive the updated prop value and reflect the change accordingly.

Working with props in Svelte allows for effective communication between components, enabling you to build more flexible and interactive applications. By following the steps outlined in this guide, you can confidently leverage props to enhance your Svelte development workflow.

Tags: Svelte, component communication, props