feat: iterable/is

README.md

@@ -339,6 +339,25 @@ ensureArrayLength(9007199254740992); // Thrown TypeError: null is not a valid ar
 
 ---
 
+### Iterable
+
+The JavaScript value which implements _iterable_ protocol
+
+#### `iterable/is`
+
+Confirms if given object is iterable, but default rejects _strings_, they're accepted if `allowString` option is passed
+
+```javascript
+const isIterable = require("type/iterable/is");
+
+isIterable([]); // true
+isIterable({}); // false
+isIterable("foo"); // false
+isIterable("foo", { allowString: true }); // true
+```
+
+---
+
 ### Date
 
 The JavaScript _Date_ instance

iterable/is.js

@@ -0,0 +1,20 @@
+// Polyfills friendly, therefore ES5 syntax
+
+"use strict";
+
+var isObject = require("../object/is");
+
+var iteratorSymbol = Symbol.iterator;
+
+if (!iteratorSymbol) {
+	throw new Error("Cannot initialize iterator/is due to Symbol.iterator not being implemented");
+}
+
+module.exports = function (value/*, options*/) {
+	if (!isObject(value)) {
+		var options = arguments[1];
+		if (!isObject(options) || !options.allowString || typeof value !== "string") return false;
+	}
+	try { return typeof value[iteratorSymbol] === "function"; }
+	catch (error) { return false; }
+};

package.json

@@ -36,6 +36,8 @@
 		"extends": "medikoo-es3",
 		"root": true,
 		"globals": {
+			"Map": true,
+			"Set": true,
 			"Symbol": true
 		},
 		"overrides": [

test/iterable/is.js

@@ -0,0 +1,50 @@
+"use strict";
+
+var assert     = require("chai").assert
+  , isIterable = require("../../iterable/is");
+
+describe("iterable/is", function () {
+	it("Should return true on array", function () { assert.equal(isIterable([]), true); });
+	it("Should return true on arguments", function () {
+		assert.equal(isIterable((function () { return arguments; })()), true);
+	});
+	it("Should by default return false on string", function () {
+		assert.equal(isIterable("foo"), false);
+	});
+	it("Should accept strings if specified", function () {
+		assert.equal(isIterable("foo", { allowString: true }), true);
+	});
+
+	if (typeof Set === "function") {
+		it("Should return true on set", function () { assert.equal(isIterable(new Set()), true); });
+	}
+	if (typeof Map === "function") {
+		it("Should return true on set", function () { assert.equal(isIterable(new Map()), true); });
+	}
+
+	it("Should return false on plain object", function () { assert.equal(isIterable({}), false); });
+	it("Should return false on function", function () {
+		assert.equal(isIterable(function () { return true; }), false);
+	});
+
+	if (typeof Object.create === "function") {
+		it("Should return false on object with no prototype", function () {
+			assert.equal(isIterable(Object.create(null)), false);
+		});
+	}
+	it("Should return false on string", function () { assert.equal(isIterable("foo"), false); });
+	it("Should return false on empty string", function () { assert.equal(isIterable(""), false); });
+	it("Should return false on number", function () { assert.equal(isIterable(123), false); });
+	it("Should return false on NaN", function () { assert.equal(isIterable(NaN), false); });
+	it("Should return false on boolean", function () { assert.equal(isIterable(true), false); });
+	if (typeof Symbol === "function") {
+		it("Should return false on symbol", function () {
+			assert.equal(isIterable(Symbol("foo")), false);
+		});
+	}
+
+	it("Should return false on null", function () { assert.equal(isIterable(null), false); });
+	it("Should return false on undefined", function () {
+		assert.equal(isIterable(void 0), false);
+	});
+});