fix(constructor): remove hasBeenInstantiated flag checks (#49)

* chore: Remove hasBeenInstantiated unit tests
* chore: adds contributing section to README.md

README.md

@@ -24,7 +24,7 @@ npm install @smartcar/auth
 ### Smartcar CDN
 
 ```html
-<script src="https://javascript-sdk.smartcar.com/2.4.0/sdk.js"></script>
+<script src="https://javascript-sdk.smartcar.com/2.4.1/sdk.js"></script>
 ```
 
 Before v2.2.0, the SDK was versioned as follows:
@@ -192,4 +192,4 @@ https://application-backend.com/page?error=access_denied&error_description=User+
 [tag-image]: https://img.shields.io/github/tag/smartcar/javascript-sdk.svg
 
 <!-- Please do not modify or remove this, it is used by the build process -->
-[version]: 2.4.0
+[version]: 2.4.1

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@smartcar/auth",
-  "version": "2.4.0",
+  "version": "2.4.1",
   "description": "javascript auth sdk for the smartcar",
   "main": "dist/npm/sdk.js",
   "license": "MIT",

src/sdk.js

@@ -131,16 +131,6 @@ class Smartcar {
    * @param {Object} options - the SDK configuration object
    */
   static _validateConstructorOptions(options) {
-    // allow only one instance of Smartcar
-    if (Smartcar._hasBeenInstantiated) {
-      throw new Error(
-        'Smartcar has already been instantiated in the window. Only one' +
-          ' instance of Smartcar can be defined.',
-      );
-    } else {
-      Smartcar._hasBeenInstantiated = true;
-    }
-
     if (!options.clientId) {
       throw new TypeError('A client ID option must be provided');
     }

test/unit/sdk.test.js

@@ -8,10 +8,6 @@ const isValidWindowOptions = (str) =>
 describe('sdk', () => {
   const CDN_ORIGIN = 'https://javascript-sdk.smartcar.com';
 
-  beforeEach(() => {
-    Smartcar._hasBeenInstantiated = false;
-  });
-
   describe('constructor', () => {
     test('throws error if constructor called without redirectUri', () => {
       expect(() => new Smartcar({clientId: 'uuid'})).toThrow(
@@ -25,16 +21,6 @@ describe('sdk', () => {
       );
     });
 
-    test('throws error if smartcar already instantiated', () => {
-      // initial instantiation
-      // eslint-disable-next-line no-new
-      new Smartcar({redirectUri: 'http://example.com', clientId: 'my-id'});
-      expect(() => new Smartcar({redirectUri: 'http://example.com', clientId: 'my-id'})).toThrow(
-        'Smartcar has already been instantiated in the window. Only one' +
-          ' instance of Smartcar can be defined.',
-      );
-    });
-
     test('throws error if using Smartcar hosting without onComplete', () => {
       expect(
         () =>