If a store is writable — i.e. it has a set method — you can bind to its value, just as you can bind to local component state.

In this example we have a writable store name and a derived store greeting. Update the <input> element:

<input bind:value={$name}>

Changing the input value will now update name and all its dependents.

We can also assign directly to store values inside a component. Add a <button> element:

<button on:click="{() => $name += '!'}">
  Add exclamation mark!
</button>

The $name += '!' assignment is equivalent to name.set($name + '!').