The readable store is a read only store. But, if it's read only, how does the value change?

Like before the first argument in readable() is the initial value of the store.

In addition, readable stores have a mandatory second argument which is a so called start stop notifier .

This function is run when someone subscribes to the store for the first time .

You can also have a clean up function as a return statement that will run when the subscribers all unsubscribe so there are 0 subscribers.

The parameter for the start stop notifier is set (same as the writable store method).

<script>
	import Output from "./Output.svelte";
</script>

<Output />

Here is an example where we console log when we subscribe and unsubscribe:

<script>
	import Output2 from "./Output2.svelte";
</script>

<Output2 />