feat(parser): add optional argument iterator

The iterator is useful in building a customized output.

index.js

@@ -1,26 +1,36 @@
 var parse = require('css/lib/parse');
 
 /**
- * Parses inline style to object (server).
+ * Parses inline style.
  *
  * Example: 'color:red' => { color: 'red' }
  *
- * @param {String} style
- * @return {Object|null}
+ * @param  {String}      style      - The inline style.
+ * @param  {Function}    [iterator] - The iterator function.
+ * @return {null|Object}
  */
-module.exports = function parseInlineStyleServer(style) {
+module.exports = function parseInlineStyle(style, iterator) {
   if (!style || typeof style !== 'string') return null;
 
   // make sure to wrap declarations in placeholder
   var declarations = parse('p{' + style + '}').stylesheet.rules[0].declarations;
-  var output = {};
+  var declaration, property, value;
 
-  declarations.forEach(function(declaration) {
-    var value = declaration.value;
-    if (value) {
-      output[declaration.property] = value;
+  var output = null;
+  var hasIterator = typeof iterator === 'function';
+
+  for (var i = 0, len = declarations.length; i < len; i++) {
+    declaration = declarations[i];
+    property = declaration.property;
+    value = declaration.value;
+
+    if (hasIterator) {
+      iterator(property, value, declaration);
+    } else if (value) {
+      output || (output = {});
+      output[property] = value;
     }
-  });
+  }
 
   return output;
 };

test/cases.js

@@ -101,7 +101,7 @@ const styles = [
   // missing value
   {
     style: 'z-index:',
-    expected: {},
+    expected: null,
   },
 
   // missing property

test/index.js

@@ -1,24 +1,45 @@
 'use strict';
 
 const assert = require('assert');
+const css = require('css');
 const cases = require('./cases');
 const parser = require('../')
 
 describe('parser', () => {
   cases.default.forEach(({ style, expected }) => {
-
+    // error case
     describe(`when style=\`${style}\``, () => {
       if (expected === Error) {
         it('throws error', () => {
           assert.throws(() => parser(style), Error);
         });
-
-      } else {
-        it(`returns ${JSON.stringify(expected)}`, () => {
-          assert.deepEqual(parser(style), expected);
-        });
+        return;
       }
+
+      // normal case
+      it(`returns ${JSON.stringify(expected)}`, () => {
+        assert.deepEqual(parser(style), expected);
+      });
+    });
+  });
+
+  describe('when iterator is passed', () => {
+    it('returns null', () => {
+      const style = cases.styles[0];
+      const iterator = () => {};
+      assert.equal(parser(style, iterator), null);
     });
 
+    it('passes the arguments: name, value, declaration', () => {
+      const style = 'color: #f00;';
+      parser(style, (name, value, declaration) => {
+        assert.equal(name, 'color');
+        assert.equal(value, '#f00');
+        assert.deepEqual(
+          declaration,
+          css.parse(`p{${style}}`).stylesheet.rules[0].declarations[0]
+        );
+      });
+    });
   });
 });