Support supplying bag to read variables from

README.md

@@ -14,6 +14,10 @@ import env from '@knpwrs/envariant';
 const DB_URI = env('DB_URI');
 // DB_URI is guaranteed to be defined at this point, as long as there is a `DB_URI` environment variable defined.
 // If there isn't a `DB_URI` variable defined then `env` will throw and this script will crash.
+
+// There is an optional second parameter that lets you supply an object to read variables from; for
+// instance, the `env` parameter in Cloudflare workers:
+const ENDPOINT = env('ENDPOINT', env);
 ```
 
 ## Installation

src/index.test.ts

@@ -14,5 +14,13 @@ test('variable defined', () => {
 });
 
 test('variable not defined', () => {
-  expect(() => env(name)).toThrow(`${name} is not defined in process.env!`);
+  expect(() => env(name)).toThrow(`${name} is not defined in environment!`);
+});
+
+test('variable defined in provided bag', () => {
+  expect(env('foo', { foo: 'bar' })).toBe('bar');
+});
+
+test('variable not defined in provided bag', () => {
+  expect(() => env('foo', {})).toThrow('foo is not defined in environment!');
 });

src/index.ts

@@ -1,8 +1,11 @@
-export default function envariant(name: string): string {
-  const value = process.env[name];
+export default function envariant(
+  name: string,
+  bag: Record<string, string | undefined> = process.env,
+): string {
+  const value = bag[name];
 
   if (!value) {
-    throw new Error(`${name} is not defined in process.env!`);
+    throw new Error(`${name} is not defined in environment!`);
   }
 
   return value;