Bump to v4.0.0.

flatMap.js

@@ -0,0 +1,30 @@
+import arrayMap from './internal/arrayMap';
+import baseFlatten from './internal/baseFlatten';
+import baseIteratee from './internal/baseIteratee';
+
+/**
+ * Creates an array of flattened values by running each element in `array`
+ * through `iteratee` and concating its result to the other mapped values.
+ * The iteratee is invoked with three arguments: (value, index|key, array).
+ *
+ * @static
+ * @memberOf _
+ * @category Array
+ * @param {Array} array The array to iterate over.
+ * @param {Function|Object|string} [iteratee=_.identity] The function invoked per iteration.
+ * @returns {Array} Returns the new array.
+ * @example
+ *
+ * function duplicate(n) {
+ *   return [n, n];
+ * }
+ *
+ * _.flatMap([1, 2], duplicate);
+ * // => [1, 1, 2, 2]
+ */
+function flatMap(array, iteratee) {
+  var length = array ? array.length : 0;
+  return length ? baseFlatten(arrayMap(array, baseIteratee(iteratee, 3))) : [];
+}
+
+export default flatMap;