Add Channel.isChannel.

README.md

@@ -173,6 +173,10 @@ These methods are similar to the equivalently named methods of `Array`.
 Create a new `Channel` with an optional buffer.  This allows an async function
 to push up to `bufferLength` values before blocking.
 
+#### Channel.isChannel(value) -> Boolean
+
+Return `true` if `value` is a channel, `false` otherwise.
+
 #### Channel.of(...values) -> Channel
 
 Pushes `values` into a new channel and then closes it.

lib/index.js

@@ -34,6 +34,8 @@ const Order = (channel) => {
   return {order, promise}
 }
 
+const prototype = {}
+
 const Channel = function (bufferLength = 0) {
   let buffered = 0
   let closed = false
@@ -102,7 +104,7 @@ const Channel = function (bufferLength = 0) {
     resolvedIndex -= index.push
   }
 
-  const readOnly = Object.freeze({
+  const readOnly = Object.assign(Object.create(prototype), {
     every: async (callbackfn, thisArg) => {
       for (;;) {
         const value = await readOnly.shift()
@@ -215,13 +217,12 @@ const Channel = function (bufferLength = 0) {
       })()
 
       return output
-    },
-
-    get value () {
-      return lastValue
     }
   })
 
+  Object.defineProperty(readOnly, `value`, {get: () => lastValue})
+  Object.freeze(readOnly)
+
   const writeOnly = Object.freeze({
     close: () =>
       new Promise((resolve, reject) => {
@@ -299,6 +300,9 @@ Channel.from = (values) => {
 Channel.of = (...values) =>
   Channel.from(values)
 
+Channel.isChannel = (arg) =>
+  prototype.isPrototypeOf(arg)
+
 Channel.select = (...methodPromises) => {
   const promise = new Promise((resolve, reject) => {
     methodPromises.forEach(async (promise) => {

test/index.js

@@ -57,6 +57,11 @@ describe(`Channel`, function () {
     })
   })
 
+  it(`isChannel`, function () {
+    assert(Channel.isChannel(Channel.of(0, 1, 2)))
+    assert(!Channel.isChannel(Array.of(0, 1, 2)))
+  })
+
   it(`of`, async function () {
     assert.deepEqual(await toArray(Channel.of(0, 1, 2)), [0, 1, 2])
   })