feat: prototype/is

README.md

@@ -94,6 +94,20 @@ ensureObject(obj); // obj
 ensureString(null); // Thrown TypeError: null is not an object
 ```
 
+#### Prototype
+
+_Prototype_ is assumed to be some constructor's `prototype` property
+
+##### `prototype/is`
+
+```javascript
+const isPrototype = require("type/prototype/is");
+
+isPrototype({}); // false
+isPrototype(Object.prototype); // true
+isPrototype(Array.prototype); // true
+```
+
 ### Tests
 
     $ npm test

prototype/is.js

@@ -0,0 +1,9 @@
+"use strict";
+
+var isObject = require("../object/is");
+
+module.exports = function (value) {
+	if (!isObject(value)) return false;
+	if (!value.constructor) return false;
+	return value.constructor.prototype === value;
+};

test/prototype/is.js

@@ -0,0 +1,39 @@
+"use strict";
+
+var assert      = require("chai").assert
+  , isPrototype = require("../../prototype/is");
+
+describe("prototype/is", function () {
+	it("Should return true on prototype", function () {
+		assert.equal(isPrototype(Object.prototype), true);
+	});
+	it("Should return false on plain object", function () {
+		assert.equal(isPrototype({}), false);
+	});
+	it("Should return false on function", function () {
+		assert.equal(isPrototype(function () { return true; }), false);
+	});
+	it("Should return false on array", function () { assert.equal(isPrototype([]), false); });
+	if (typeof Object.create === "function") {
+		it("Should return false on object with no prototype", function () {
+			assert.equal(isPrototype(Object.create(null)), false);
+		});
+	}
+	it("Should return false on string", function () { assert.equal(isPrototype("foo"), false); });
+	it("Should return false on empty string", function () {
+		assert.equal(isPrototype(""), false);
+	});
+	it("Should return false on number", function () { assert.equal(isPrototype(123), false); });
+	it("Should return false on NaN", function () { assert.equal(isPrototype(NaN), false); });
+	it("Should return false on boolean", function () { assert.equal(isPrototype(true), false); });
+	if (typeof Symbol === "function") {
+		it("Should return false on symbol", function () {
+			assert.equal(isPrototype(Symbol("foo")), false);
+		});
+	}
+
+	it("Should return false on null", function () { assert.equal(isPrototype(null), false); });
+	it("Should return false on undefined", function () {
+		assert.equal(isPrototype(void 0), false);
+	});
+});