Merge pull request #143 from knockout/bmh/observable-symbol-polyfill

observable) add polyfill for Symbol.observable

Author: brianmhunt

packages/observable/spec/subscribableBehaviors.ts

@@ -17,6 +17,12 @@ describe('Subscribable', function () {
     expect(isSubscribable(null)).toEqual(false)
   })
 
+  it('creates/has a Symbol.observable', () => {
+    const sub = new subscribable()
+    expect(Symbol.observable).toEqual(Symbol.for('@tko/Symbol.observable'))
+    expect(sub[Symbol.observable]()).toBe(sub)
+  })
+
   it('Should be able to notify subscribers', function () {
     var instance = new subscribable()
     var notifiedValue

packages/observable/src/subscribable.ts

@@ -14,6 +14,11 @@ export { isSubscribable } from './subscribableSymbol'
 // subscribed.
 export const LATEST_VALUE = Symbol('Knockout latest value')
 
+
+if (!Symbol.observable) {
+  Symbol.observable = Symbol.for('@tko/Symbol.observable')
+}
+
 export function subscribable () {
   Object.setPrototypeOf(this, ko_subscribable_fn)
   ko_subscribable_fn.init(this)