Move `Number` polyfills into the `/polyfills/` directory

Reviewed By: vjeux

Differential Revision: D3223317

fb-gh-sync-id: a49a14f217b27d6542b65c4780c557e73da2443f
fbshipit-source-id: a49a14f217b27d6542b65c4780c557e73da2443f

react-packager/src/Resolver/polyfills/Number.es6.js

@@ -10,6 +10,21 @@
  * @polyfill
  */
 
+if (Number.EPSILON === undefined) {
+  Object.defineProperty(Number, 'EPSILON', {
+    value: Math.pow(2, -52),
+  });
+}
+if (Number.MAX_SAFE_INTEGER === undefined) {
+  Object.defineProperty(Number, 'MAX_SAFE_INTEGER', {
+    value: Math.pow(2, 53) - 1,
+  });
+}
+if (Number.MIN_SAFE_INTEGER === undefined) {
+  Object.defineProperty(Number, 'MIN_SAFE_INTEGER', {
+    value: -(Math.pow(2, 53) - 1),
+  });
+}
 if (!Number.isNaN) {
   // https://github.com/dherman/tc39-codex-wiki/blob/master/data/es6/number/index.md#polyfill-for-numberisnan
   const globalIsNaN = global.isNaN;

react-packager/src/Resolver/polyfills/__tests__/Number.es6-test.js

@@ -12,6 +12,40 @@
 jest.autoMockOff();
 
 describe('Number (ES6)', () => {
+  describe('EPSILON', () => {
+    beforeEach(() => {
+      delete Number.EPSILON;
+      jest.resetModuleRegistry();
+      require('../Number.es6');
+    });
+    it('is 2^(-52)', () => {
+      expect(Number.EPSILON).toBe(Math.pow(2, -52));
+    });
+    it('can be used to test equality', () => {
+      // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/EPSILON#Testing_equality
+      expect(Number.EPSILON).toBeGreaterThan(Math.abs(0.2 - 0.3 + 0.1));
+    });
+  });
+  describe('MAX_SAFE_INTEGER', () => {
+    beforeEach(() => {
+      delete Number.MAX_SAFE_INTEGER;
+      jest.resetModuleRegistry();
+      require('../Number.es6');
+    });
+    it('is 2^53 - 1', () => {
+      expect(Number.MAX_SAFE_INTEGER).toBe(Math.pow(2, 53) - 1);
+    });
+  });
+  describe('MIN_SAFE_INTEGER', () => {
+    beforeEach(() => {
+      delete Number.MIN_SAFE_INTEGER;
+      jest.resetModuleRegistry();
+      require('../Number.es6');
+    });
+    it('is -(2^53 - 1)', () => {
+      expect(Number.MIN_SAFE_INTEGER).toBe(-(Math.pow(2, 53) - 1));
+    });
+  });
   describe('isNaN()', () => {
     // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isNaN#Examples
     beforeEach(() => {