From 95419c5dde80c477f9559224b6938d924d225135 Mon Sep 17 00:00:00 2001
From: Sebastian Markbage <sema@fb.com>
Date: Thu, 19 Oct 2017 00:40:16 -0700
Subject: [PATCH] Authoritative brand checking library

Can be used without any dependency on React. Plausible replacement for
React.isValidElement.
---
 packages/react-is/README.md    | 33 +++++++++++++++++
 packages/react-is/index.js     | 67 ++++++++++++++++++++++++++++++++++
 packages/react-is/package.json | 12 ++++++
 3 files changed, 112 insertions(+)
 create mode 100644 packages/react-is/README.md
 create mode 100644 packages/react-is/index.js
 create mode 100644 packages/react-is/package.json

diff --git a/packages/react-is/README.md b/packages/react-is/README.md
new file mode 100644
index 0000000000000..05dca2624be01
--- /dev/null
+++ b/packages/react-is/README.md
@@ -0,0 +1,33 @@
+# `react-is`
+
+This package allows you to test arbitrary values and see if they're a particular React type, e.g. React Elements.
+
+## Usage
+
+```js
+import React from 'react';
+import {isElement} from 'react-is';
+isElement(<div />); // true
+```
+
+```js
+import React from 'react';
+import {isFragment} from 'react-is';
+isFragment(<></>); // true
+```
+
+```js
+import React from 'react';
+import {createPortal} from 'react-dom';
+import {isPortal} from 'react-is';
+isPortal(createPortal(<div />, document.body)); // true
+```
+
+```js
+import React from 'react';
+import {createPortal} from 'react-dom';
+import {typeOf} from 'react-is';
+typeOf(<div />); // "ReactElement"
+typeOf(<></>); // "ReactFragment"
+typeOf(createPortal(<div />, document.body)); // "ReactPortal"
+```
diff --git a/packages/react-is/index.js b/packages/react-is/index.js
new file mode 100644
index 0000000000000..670df04aa913a
--- /dev/null
+++ b/packages/react-is/index.js
@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+var REACT_ELEMENT_TYPE;
+var REACT_COROUTINE_TYPE;
+var REACT_YIELD_TYPE;
+var REACT_PORTAL_TYPE;
+var REACT_FRAGMENT_TYPE;
+if (typeof Symbol === 'function' && Symbol.for) {
+  REACT_ELEMENT_TYPE = Symbol.for('react.element');
+  REACT_COROUTINE_TYPE = Symbol.for('react.coroutine');
+  REACT_YIELD_TYPE = Symbol.for('react.yield');
+  REACT_PORTAL_TYPE = Symbol.for('react.portal');
+  REACT_FRAGMENT_TYPE = Symbol.for('react.fragment');
+} else {
+  REACT_ELEMENT_TYPE = 0xeac7;
+  REACT_COROUTINE_TYPE = 0xeac8;
+  REACT_YIELD_TYPE = 0xeac9;
+  REACT_PORTAL_TYPE = 0xeaca;
+  REACT_FRAGMENT_TYPE = 0xeacb;
+}
+
+function is(object, type) {
+  return (
+    typeof object === 'object' && object !== null && object.$$typeof === type
+  );
+}
+
+module.exports = {
+  typeOf(object) {
+    switch (typeof object === 'object' && object !== null && object.$$typeof) {
+      case REACT_ELEMENT_TYPE:
+        return 'ReactElement';
+      case REACT_COROUTINE_TYPE:
+        return 'ReactCoroutine';
+      case REACT_YIELD_TYPE:
+        return 'ReactYield';
+      case REACT_PORTAL_TYPE:
+        return 'ReactPortal';
+      case REACT_FRAGMENT_TYPE:
+        return 'ReactFragment';
+      default:
+        return undefined;
+    }
+  },
+  isElement(object) {
+    return is(object, REACT_ELEMENT_TYPE);
+  },
+  isCoroutine(object) {
+    return is(object, REACT_COROUTINE_TYPE);
+  },
+  isYield(object) {
+    return is(object, REACT_YIELD_TYPE);
+  },
+  isPortal(object) {
+    return is(object, REACT_PORTAL_TYPE);
+  },
+  isFragment(object) {
+    return is(object, REACT_FRAGMENT_TYPE);
+  },
+};
diff --git a/packages/react-is/package.json b/packages/react-is/package.json
new file mode 100644
index 0000000000000..b705d03941257
--- /dev/null
+++ b/packages/react-is/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "react-is",
+  "description": "Brand checking of React Elements.",
+  "keywords": ["react"],
+  "version": "1.0.0",
+  "homepage": "https://reactjs.org/",
+  "bugs": "https://github.com/facebook/react/issues",
+  "license": "MIT",
+  "files": ["index.js"],
+  "main": "index.js",
+  "repository": "facebook/react"
+}