feat: natural-number/ensure

README.md

@@ -215,7 +215,7 @@ Otherwise `TypeError` is thrown.
 const ensureSafeInteger = require("type/safe-integer/ensure");
 
 ensureSafeInteger(12.93); // "12"
-ensureSafeInteger(9007199254740992); // Thrown TypeError: null is not a number
+ensureSafeInteger(9007199254740992); // Thrown TypeError: null is not a safe integer
 ```
 
 ---
@@ -234,6 +234,18 @@ coerceToNaturalNumber(-120); // null
 coerceToNaturalNumber(null); // null
 ```
 
+##### `natural-number/ensure`
+
+If given argument is a natural number coercible value (via [`natural-number/coerce`](#natural-numbercoerce)) returns result number.
+Otherwise `TypeError` is thrown.
+
+```javascript
+const ensureNaturalNumber = require("type/natural-number/ensure");
+
+ensureNaturalNumber(12.93); // "12"
+ensureNaturalNumber(-230); // Thrown TypeError: null is not a natural number
+```
+
 ---
 
 ### Array

natural-number/ensure.js

@@ -0,0 +1,10 @@
+"use strict";
+
+var resolveException = require("../lib/resolve-exception")
+  , coerce           = require("./coerce");
+
+module.exports = function (value/*, options*/) {
+	var coerced = coerce(value);
+	if (coerced !== null) return coerced;
+	return resolveException(value, "%v is not a natural number", arguments[1]);
+};

test/natural-number/ensure.js

@@ -0,0 +1,19 @@
+"use strict";
+
+var assert              = require("chai").assert
+  , ensureNaturalNumber = require("../../natural-number/ensure");
+
+describe("natural-numbe/ensure", function () {
+	it("Should return coerced value", function () {
+		assert.equal(ensureNaturalNumber("12.23"), 12);
+	});
+	it("Should crash on no value", function () {
+		try {
+			ensureNaturalNumber(-20);
+			throw new Error("Unexpected");
+		} catch (error) {
+			assert.equal(error.name, "TypeError");
+			assert.equal(error.message, "-20 is not a natural number");
+		}
+	});
+});