feat: array/ensure

README.md

@@ -122,6 +122,17 @@ isArray({}); // false
 isArray("foo"); // false
 ```
 
+##### `array/ensure`
+
+If given argument is an array, it is returned back. Otherwise `TypeError` is thrown.
+
+```javascript
+const ensureArray = require("type/array/ensure");
+
+ensureArray(["foo"]); // ["foo"]
+ensureArray("foo"); // Thrown TypeError: null is not a regular expression object
+```
+
 #### RegExp
 
 The JavaScript _RegExp_ instance

array/ensure.js

@@ -0,0 +1,9 @@
+"use strict";
+
+var resolveException = require("../lib/resolve-exception")
+  , is               = require("./is");
+
+module.exports = function (value/*, options*/) {
+	if (is(value)) return value;
+	return resolveException(value, "%v is not an array object", arguments[1]);
+};

test/array/ensure.js

@@ -0,0 +1,20 @@
+"use strict";
+
+var assert      = require("chai").assert
+  , ensureArray = require("../../array/ensure");
+
+describe("array/ensure", function () {
+	it("Should return input value", function () {
+		var value = [];
+		assert.equal(ensureArray(value), value);
+	});
+	it("Should crash on invalid value", function () {
+		try {
+			ensureArray(null);
+			throw new Error("Unexpected");
+		} catch (error) {
+			assert.equal(error.name, "TypeError");
+			assert(error.message.includes("is not an array object"));
+		}
+	});
+});