Add save method

lib/index.js

@@ -8,5 +8,6 @@ module.exports = {
     parse: require('./parse'),
     assign: require('./assign'),
     load: require('./load'),
-    stringify: require('./stringify')
+    stringify: require('./stringify'),
+    save: require('./save')
 };

lib/save.js

@@ -0,0 +1,26 @@
+'use strict';
+
+const fs = require('fs');
+const promisify = require('es6-promisify');
+const stringify = require('./stringify');
+
+const writeFile = promisify(fs.writeFile);
+
+/**
+ * Save normalized declaration to target format
+ *
+ * @param   {String}    filename        Filename for save declaration
+ * @param   {BemCell[]} cells           Normalized declaraions
+ * @param   {Object}    opts            Addtional options
+ * @param   {String}    opts.format     Format for save declaration
+ * @param   {String}    opts.exportType The appointment of a modular system
+ * @returns {Promise.<void>}
+ */
+module.exports = (filename, cells, opts) => {
+    const data = stringify(cells, Object.assign({
+        format: 'v2',
+        exportType: 'cjs'
+    }, opts));
+
+    return writeFile(data)
+}