Add is.nodeStream() (#34)

package.json

@@ -49,9 +49,11 @@
 	"devDependencies": {
 		"@types/jsdom": "^2.0.31",
 		"@types/node": "^8.0.47",
+		"@types/tempy": "^0.1.0",
 		"ava": "*",
 		"del-cli": "^1.1.0",
 		"jsdom": "^9.12.0",
+		"tempy": "^0.2.1",
 		"tslint": "^5.8.0",
 		"tslint-xo": "^0.3.0",
 		"typescript": "^2.6.1"

readme.md

@@ -211,6 +211,16 @@ is.inRange(3, 10);
 
 Returns `true` if `value` is a DOM Element.
 
+##### .nodeStream(value)
+
+Returns `true` if `value` is a Node.js [stream](https://nodejs.org/api/stream.html).
+
+```js
+const fs = require('fs');
+is.nodeStream(fs.createReadStream('unicorn.png'));
+//=> true
+```
+
 ##### .infinite(value)
 
 Check if `value` is `Infinity` or `-Infinity`.

source/index.ts

@@ -238,6 +238,8 @@ namespace is { // tslint:disable-line:no-namespace
 	export const domElement = (value: any) => object(value) && value.nodeType === NODE_TYPE_ELEMENT && string(value.nodeName) &&
 		!plainObject(value) && DOM_PROPERTIES_TO_CHECK.every(property => property in value);
 
+	export const nodeStream = (value: any) => !nullOrUndefined(value) && isObject(value) && function_(value.pipe);
+
 	export const infinite = (value: any) => value === Infinity || value === -Infinity;
 
 	const isAbsoluteMod2 = (value: number) => (rem: number) => integer(rem) && Math.abs(rem % 2) === value;

source/tests/test.ts

@@ -1,4 +1,8 @@
+import * as fs from 'fs';
+import * as net from 'net';
+import * as Stream from 'stream';
 import * as util from 'util';
+import * as tempy from 'tempy';
 import test, {TestContext, Context} from 'ava';
 import {jsdom} from 'jsdom';
 import m from '..';
@@ -286,7 +290,8 @@ const types = new Map<string, Test>([
 			'canvas',
 			'script'
 		].map(createDomElement) }
-	], ['non-domElements', {
+	],
+	['non-domElements', {
 		is: value => !m.domElement(value),
 		fixtures: [
 			document.createTextNode('data'),
@@ -297,6 +302,20 @@ const types = new Map<string, Test>([
 			document.createDocumentFragment()
 		]
 	}],
+	['nodeStream', {
+		is: m.nodeStream,
+		fixtures: [
+			fs.createReadStream('readme.md'),
+			fs.createWriteStream(tempy.file()),
+			new net.Socket(),
+			new Stream.Duplex(),
+			new Stream.PassThrough(),
+			new Stream.Readable(),
+			new Stream.Transform(),
+			new Stream.Stream(),
+			new Stream.Writable()
+		]
+	}],
 	['infinite', {
 		is:  m.infinite,
 		fixtures: [
@@ -641,6 +660,10 @@ test('is.domElement', t => {
 	t.false(m.domElement({nodeType: 1, nodeName: 'div'}));
 });
 
+test('is.nodeStream', t => {
+	testType(t, 'nodeStream');
+});
+
 test('is.infinite', t => {
 	testType(t, 'infinite', ['number']);
 });