snapshot of https://github.com/tldraw/tldraw.git (main, 2026-09-23; blobs > 131072B omitted)

packages/state/src/lib/isSignal.ts

@@ -0,0 +1,34 @@
+import { _Atom } from './Atom'
+import { _Computed } from './Computed'
+import { Signal } from './types'
+
+/**
+ * Type guard function that determines whether a value is a signal (either an Atom or Computed).
+ *
+ * This utility function is helpful when working with mixed data types and you need to
+ * differentiate between regular values and reactive signal containers. It returns `true`
+ * if the provided value is either an atomic signal created with `atom()` or a computed
+ * signal created with `computed()`.
+ *
+ * @param value - The value to check, can be of any type
+ * @returns `true` if the value is a Signal (Atom or Computed), `false` otherwise
+ *
+ * @example
+ * ```ts
+ * import { atom, computed, isSignal } from '@tldraw/state'
+ *
+ * const count = atom('count', 5)
+ * const doubled = computed('doubled', () => count.get() * 2)
+ * const regularValue = 'hello'
+ *
+ * console.log(isSignal(count))        // true
+ * console.log(isSignal(doubled))      // true
+ * console.log(isSignal(regularValue)) // false
+ * console.log(isSignal(null))         // false
+ * ```
+ *
+ * @public
+ */
+export function isSignal(value: any): value is Signal<any> {
+	return value instanceof _Atom || value instanceof _Computed
+}