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Scope Slots

Scope slots are typed tokens for storing values on a scope and resolving them through the parent chain.

Creating Slots

Create a slot with ScopeSlot.create<T>():

import { createScope, ScopeSlot } from "@kayahr/scope";

const localeSlot = ScopeSlot.create<string>();

const root = createScope();
root.set(localeSlot, "en");

const child = createScope(root);
child.get(localeSlot);  // undefined
child.find(localeSlot); // "en"

child.set(localeSlot, "de");
child.get(localeSlot);  // "de"
child.find(localeSlot); // "de"

Slots are compared by identity, not by name.

Lookup

  • scope.set(slot, value) stores a local value on one scope.
  • scope.get(slot) reads only the local value from that scope.
  • scope.has(slot) checks whether that scope has a local value.
  • scope.delete(slot) removes only the local value from that scope.
  • scope.find(slot) walks up the parent chain and returns the nearest stored value.

scope.get(...) and scope.find(...) return undefined when no value exists on a live scope.

Disposal

Disposed scopes are no longer usable. Accessing or modifying slot values on them throws a ScopeError.