Rest parameters in Svelte - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are rest parameters in Svelte?

Rest parameters allow a component to collect all extra props passed to it into a single object. This helps to pass down or handle unknown or additional attributes easily.

beginner

How do you declare rest parameters in a Svelte component?

You use the $$restProps variable inside the component script. It automatically contains all props not explicitly declared.

intermediate

Why use rest parameters instead of declaring all props explicitly?

Rest parameters let you handle extra or unknown props without listing them all. This is useful for forwarding attributes like <code>class</code>, <code>id</code>, or event handlers.

beginner

How can you apply rest parameters to an HTML element inside a Svelte component?

You spread $$restProps on the element using {...$$restProps}. This passes all extra props to that element.

intermediate

What happens if you pass a prop to a Svelte component that is not declared and you do not use rest parameters?

The extra prop is ignored and not accessible inside the component. Using $$restProps lets you capture those props.

In Svelte, which variable holds all extra props passed to a component?

A props

B $$extraProps

C restParams

D $$restProps

The special variable $$restProps contains all props not explicitly declared in the component.

How do you pass all extra props to an HTML element inside a Svelte component?

A {...$$restProps}

B {...attributes}

C {...extra}

D {...props}

You spread $$restProps on the element like {...$$restProps} to forward all extra props.

What is a common use case for rest parameters in Svelte components?

A To declare all props explicitly

B To collect and forward unknown props

C To prevent passing props

D To handle events only

Rest parameters help collect unknown or extra props so you can forward or handle them flexibly.

If a prop is not declared and $$restProps is not used, what happens to that prop?

A It is ignored inside the component

B It is accessible normally

C It causes an error

D It is automatically forwarded

Props not declared and not captured by $$restProps are ignored inside the component.

Which of these is NOT true about $$restProps in Svelte?

A It is reactive

B It contains all undeclared props

C It must be declared manually

D It can be spread on elements

$$restProps is a built-in variable and does not need manual declaration.

Explain how rest parameters work in Svelte components and why they are useful.

Think about how you can pass extra HTML attributes without declaring each one.

Describe how to use $$restProps to forward all extra props to a button element inside a Svelte component.

Remember the spread syntax inside the element tag.