Part 4 / Advanced loading / Using parent data

As we saw in the introduction to layout data, +page.svelte and +layout.svelte components have access to everything returned from their parent load functions.

Occasionally it's useful for the load functions themselves to access data from their parents. This can be done with await parent().

To show how it works, we'll sum two numbers that come from different load functions. First, return some data from src/routes/+layout.server.js:

export function load() {
	return { a: 1 };
}

Then, get that data in src/routes/sum/+layout.js:

export async function load({ parent }) {
	const { a } = await parent();
	return { b: a + 1 };
}

Notice that a universal load function can get data from a parent server load function. The reverse is not true — a server load function can only get parent data from another server load function.

Finally, in src/routes/sum/+page.js, get parent data from both load functions:

export async function load({ parent }) {
	const { a, b } = await parent();
	return { c: a + b };
}

Take care not to introduce waterfalls when using await parent(). If you can fetch other data that is not dependent on parent data, do that first.