fix(checks): fix #77, update & minor optimization isPlainObject()

- add/update tests
- add AUTHORS.md

packages/checks/AUTHORS.md

@@ -0,0 +1,8 @@
+## Maintainer
+
+-   Karsten Schmidt (@postspectacular)
+
+## Contributors
+
+-   Gavin Cannizzaro (@gavinpc-mindgrub)
+-   Jay Zawrotny (@andrew8er)

packages/checks/src/is-plain-object.ts

@@ -1,4 +1,4 @@
-const OBJP = Object.getPrototypeOf({});
+const OBJP = Object.getPrototypeOf;
 
 /**
  * Similar to `isObject()`, but also checks if prototype is that of
@@ -7,9 +7,10 @@ const OBJP = Object.getPrototypeOf({});
  * @param x
  */
 export const isPlainObject = (x: any): x is object => {
-    let proto;
+    let p;
     return (
-        Object.prototype.toString.call(x) === "[object Object]" &&
-        ((proto = Object.getPrototypeOf(x)), proto === null || proto === OBJP)
+        x != null &&
+        typeof x === "object" &&
+        ((p = OBJP(x)) === null || OBJP(p) === null)
     );
 };

packages/checks/test/index.ts

@@ -1,5 +1,5 @@
 import * as assert from "assert";
-
+import * as vm from "vm";
 import { existsAndNotNull } from "../src/exists-not-null";
 import { implementsFunction } from "../src/implements-function";
 import { isArray } from "../src/is-array";
@@ -12,8 +12,7 @@ import { isSymbol } from "../src/is-symbol";
 import { isTransferable } from "../src/is-transferable";
 import { isTypedArray } from "../src/is-typedarray";
 
-describe("checks", function () {
-
+describe("checks", function() {
     it("existsAndNotNull", () => {
         assert.ok(existsAndNotNull([]), "empty array");
         assert.ok(existsAndNotNull(new Uint8Array(1)), "typedarray");
@@ -66,7 +65,7 @@ describe("checks", function () {
     });
 
     it("isObject", () => {
-        function Foo() { };
+        function Foo() {}
         assert.ok(isObject([]), "empty array");
         assert.ok(isObject(new Uint8Array(1)), "typedarray");
         assert.ok(isObject({}), "obj");
@@ -79,17 +78,25 @@ describe("checks", function () {
     });
 
     it("isPlainObject", () => {
-        function Foo() { };
+        const ctxClass = vm.runInNewContext("class A {}; new A();");
+        const ctxObj = vm.runInNewContext("({})");
+
+        function Foo() {}
+
         assert.ok(isPlainObject({}), "obj");
+        assert.ok(isPlainObject(Object.create(null)), "obj");
         assert.ok(isPlainObject(new Object()), "obj ctor");
         assert.ok(!isPlainObject(Foo), "fn");
+        assert.ok(!isPlainObject((function*() {})()), "generator");
         assert.ok(!isPlainObject(new Foo()), "class");
         assert.ok(!isPlainObject([]), "empty array");
         assert.ok(!isPlainObject(new Uint8Array(1)), "typedarray");
         assert.ok(!isPlainObject("[]"), "string");
         assert.ok(!isPlainObject(0), "zero");
         assert.ok(!isPlainObject(null), "null");
         assert.ok(!isPlainObject(undefined), "null");
+        assert.ok(isPlainObject(ctxObj), "vm ctx obj");
+        assert.ok(!isPlainObject(ctxClass), "vm ctx class");
     });
 
     it("isString", () => {
@@ -142,5 +149,4 @@ describe("checks", function () {
         assert.ok(!isTransferable(null), "null");
         assert.ok(!isTransferable(undefined), "undefined");
     });
-
 });