feat: thenable/is

README.md

@@ -552,6 +552,24 @@ ensureRegExp("foo"); // Thrown TypeError: null is not a regular expression objec
 
 ---
 
+#### Thenable
+
+The JavaScript _thenable_ object (an object with `then` method)
+
+##### `thenable/is`
+
+Confirms if given object is a _thenable_
+
+```javascript
+const isThenable = require("type/thenable/is");
+
+isThenable(Promise.resolve()); // true
+isThenable({ then: () => {} }); // true
+isThenable({}); // false
+```
+
+---
+
 ### Error
 
 The JavaScript _Error_ instance

test/thenable/is.js

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

thenable/is.js

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