Add is.asyncIterable (#59)

readme.md

@@ -209,6 +209,7 @@ Returns `true` if `value` is a [safe integer](https://developer.mozilla.org/en-U
 An object is plain if it's created by either `{}`, `new Object()`, or `Object.create(null)`.
 
 ##### .iterable(value)
+##### .asyncIterable(value)
 ##### .class(value)
 
 Returns `true` for instances created by a ES2015 class.

source/index.ts

@@ -136,6 +136,7 @@ namespace is { // tslint:disable-line:no-namespace
 	export const nullOrUndefined = (value: any): value is null | undefined => null_(value) || undefined(value);
 	export const object = (value: any): value is object => !nullOrUndefined(value) && (function_(value) || isObject(value));
 	export const iterable = (value: any): value is IterableIterator<any> => !nullOrUndefined(value) && function_(value[Symbol.iterator]);
+	export const asyncIterable = (value: any): value is AsyncIterableIterator<any> => !nullOrUndefined(value) && function_(value[Symbol.asyncIterator]);
 	export const generator = (value: any): value is Generator => iterable(value) && function_(value.next) && function_(value.throw);
 
 	export const nativePromise = (value: any): value is Promise<any> =>

source/tests/test.ts

@@ -10,6 +10,7 @@ import ZenObservable from 'zen-observable';
 import m from '..';
 
 const isNode8orHigher = Number(process.versions.node.split('.')[0]) >= 8;
+const isNode10orHigher = Number(process.versions.node.split('.')[0]) >= 10;
 
 class PromiseSubclassFixture<T> extends Promise<T> {}
 class ErrorSubclassFixture extends Error {}
@@ -603,6 +604,21 @@ test('is.iterable', t => {
 	t.false(m.iterable({}));
 });
 
+if (isNode10orHigher) {
+	test('is.asyncIterable', t => {
+		t.true(m.asyncIterable({
+			[Symbol.asyncIterator]: () => {} // tslint:disable-line:no-empty
+		}));
+
+		t.false(m.asyncIterable(null));
+		t.false(m.asyncIterable(undefined));
+		t.false(m.asyncIterable(0));
+		t.false(m.asyncIterable(NaN));
+		t.false(m.asyncIterable(Infinity));
+		t.false(m.asyncIterable({}));
+	});
+}
+
 test('is.class', t => {
 	class Foo {} // tslint:disable-line
 	const classDeclarations = [

tsconfig.json

@@ -6,7 +6,8 @@
 			"dom",
 			"es2015",
 			"es2016",
-			"es2017.sharedmemory"
+			"es2017.sharedmemory",
+			"esnext.asynciterable"
 		],
 		"module": "commonjs",
 		"moduleResolution": "node",