Bump to v4.1.0.

_indexOfNaN.js

@@ -0,0 +1,23 @@
+/**
+ * Gets the index at which the first occurrence of `NaN` is found in `array`.
+ *
+ * @private
+ * @param {Array} array The array to search.
+ * @param {number} fromIndex The index to search from.
+ * @param {boolean} [fromRight] Specify iterating from right to left.
+ * @returns {number} Returns the index of the matched `NaN`, else `-1`.
+ */
+function indexOfNaN(array, fromIndex, fromRight) {
+  var length = array.length,
+      index = fromIndex + (fromRight ? 0 : -1);
+
+  while ((fromRight ? index-- : ++index < length)) {
+    var other = array[index];
+    if (other !== other) {
+      return index;
+    }
+  }
+  return -1;
+}
+
+export default indexOfNaN;