Remove babel, use native generators, update readme, bump version

Author: jacobp100

README.md

@@ -1,6 +1,6 @@
 # css-class-generator
 
-Generates a sequential valid css class.
+Generates a sequential, valid CSS class, generating the next smallest class names possible.
 
 ```bash
 npm install --save css-class-generator
@@ -10,26 +10,23 @@ npm install --save css-class-generator
 
 `cssNameGenerator(prefix = '')` -> iterator
 
-Supports a legacy iteration mode (just an object with a function `next`).
+Will throw if prefix is not a valid class name (unless the prefix is `-`). The exception will be thrown when the first value is being yielded.
 
-Use `.` as a prefix if you want real css class names.
+Class names are generated without a leading `.`.
 
-# Example
-
-ES5:
+It uses generators, so you'll have to be using a version of node that supports this.
 
-```js
-const cssNameGenerator = require('css-class-generator');
-var generator = cssNameGenerator('prefix-');
-generator.next() // { value: 'prefix-A', done: false }
-generator.next() // { value: 'prefix-B', done: false }
-```
-
-ES6:
+# Example
 
 ```js
 const cssNameGenerator = require('css-class-generator');
 for (let value of cssNameGenerator()) {
   // 'A', 'B', ...
 }
+for (let value of cssNameGenerator('-')) {
+  // '-A', '-B', ...
+}
+for (let value of cssNameGenerator('custom-namespace-')) {
+  // You get the idea...
+}
 ```

src/index.js

@@ -51,7 +51,13 @@ function* firstTwoChars() {
   yield* appendGenerator(firstCharacters, secondCharacters());
 }
 
+const validIdent = /^-?[_a-z][_a-z0-9-]*$/i;
+
 module.exports = function* cssNameGenerator(prefix) {
+  if (prefix && prefix !== '-' && !validIdent.test(prefix)) {
+    throw new Error(`Expected prefix (${prefix}) to be a valid css class name`);
+  }
+
   if (!prefix) {
     yield* firstCharacters();
     yield* firstTwoChars();

test/index.js

@@ -31,3 +31,12 @@ test('generate name with other prefix', t => {
     t.true(isValid, `Expected ${value} to be a valid css selector`);
   }
 });
+
+test('allows hyphen for class name', t => {
+  t.notThrows(() => { cssNameGenerator('-').next(); });
+});
+
+test('throws for invalid class name', t => {
+  t.throws(() => { cssNameGenerator('--').next(); });
+  t.throws(() => { cssNameGenerator('0').next(); });
+});