Add missing files.

Author: matthargett

src/utils/isPlainObject.js

@@ -0,0 +1,16 @@
+/**
+ * @param {any} obj The object to inspect.
+ * @returns {boolean} True if the argument appears to be a plain object.
+ */
+export default function isPlainObject(obj) {
+    if (typeof obj !== 'object' || obj === null) return false
+  
+    let prototypeOfObj = Object.getPrototypeOf(obj)
+    let proto = obj
+    while (Object.getPrototypeOf(proto) !== null) {
+      proto = Object.getPrototypeOf(proto)
+  
+    }
+  
+    return prototypeOfObj === proto
+  }

test/utils/isPlainObject.spec.js

@@ -0,0 +1,20 @@
+import isPlainObject from '../../src/utils/isPlainObject'
+import vm from 'vm'
+describe('isPlainObject', () => {
+  it('returns true only if plain object', () => {
+    function Test() {
+      this.prop = 1
+    }
+
+    const sandbox = { fromAnotherRealm: false }
+    vm.runInNewContext('fromAnotherRealm = {}', sandbox)
+
+    expect(isPlainObject(sandbox.fromAnotherRealm)).toBe(true)
+    expect(isPlainObject(new Test())).toBe(false)
+    expect(isPlainObject(new Date())).toBe(false)
+    expect(isPlainObject([ 1, 2, 3 ])).toBe(false)
+    expect(isPlainObject(null)).toBe(false)
+    expect(isPlainObject()).toBe(false)
+    expect(isPlainObject({ 'x': 1, 'y': 2 })).toBe(true)
+  })
+})