Improve code quality and write tests

node_modules/lodash/_baseMap.js

@@ -0,0 +1,22 @@
+var baseEach = require('./_baseEach'),
+    isArrayLike = require('./isArrayLike');
+
+/**
+ * The base implementation of `_.map` without support for iteratee shorthands.
+ *
+ * @private
+ * @param {Array|Object} collection The collection to iterate over.
+ * @param {Function} iteratee The function invoked per iteration.
+ * @returns {Array} Returns the new mapped array.
+ */
+function baseMap(collection, iteratee) {
+  var index = -1,
+      result = isArrayLike(collection) ? Array(collection.length) : [];
+
+  baseEach(collection, function(value, key, collection) {
+    result[++index] = iteratee(value, key, collection);
+  });
+  return result;
+}
+
+module.exports = baseMap;