feat: reg-exp/ensure

README.md

@@ -122,6 +122,17 @@ isRegExp({}); // false
 isRegExp("foo"); // false
 ```
 
+##### `reg-exp/ensure`
+
+If given argument is a regular expression object, it is returned back. Otherwise `TypeError` is thrown.
+
+```javascript
+const ensureRegExp = require("type/reg-exp/ensure");
+
+ensureRegExp(/foo/); // /foo/
+ensureRegExp("foo"); // Thrown TypeError: null is not a regular expression object
+```
+
 ### Tests
 
     $ npm test

reg-exp/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 a regular expression object", arguments[1]);
+};

test/reg-exp/ensure.js

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