Add isPlainObject validator

index.js

@@ -3,6 +3,7 @@
 const createError = require("create-error");
 const assureArray = require("assure-array");
 const defaultValue = require("default-value");
+const isPlainObj = require("is-plain-obj");
 const util = require("util");
 
 let ValidationError = createError("ValidationError", { path: [] });
@@ -139,6 +140,12 @@ function validateArguments(args, rules) {
 	aggregrateErrors(errors);
 }
 
+function isPlainObject(value) {
+	if (!isPlainObj(value)) {
+		throw new ValidationError("Must be a plain object (eg. object literal)");
+	}
+}
+
 module.exports = {
 	validateArguments: validateArguments,
 	validateValue: function (value, rules) {
@@ -148,7 +155,7 @@ module.exports = {
 	},
 	validateOptions: function (args, optionsRules) {
 		return validateArguments(args, [
-			["options", optionsRules]
+			["options", isPlainObject].concat(assureArray(optionsRules))
 		]);
 	},
 	ValidationError: ValidationError,
@@ -183,6 +190,7 @@ module.exports = {
 			throw new ValidationError("Must be a Buffer object");
 		}
 	},
+	isPlainObject: isPlainObject,
 	either: function (...alternatives) {
 		if (alternatives.length === 0) {
 			throw new Error("Must specify at least one alternative");

package.json

@@ -8,6 +8,7 @@
   "dependencies": {
     "assure-array": "^1.0.0",
     "create-error": "^0.3.1",
-    "default-value": "^1.0.0"
+    "default-value": "^1.0.0",
+    "is-plain-obj": "^2.0.0"
   }
 }