Combine _.indexOf and _.lastIndexOf

Author: jridgewell

underscore.js

@@ -603,40 +603,8 @@
     return result;
   };
 
-  // Return the position of the first occurrence of an item in an array,
-  // or -1 if the item is not included in the array.
-  // If the array is large and already in sort order, pass `true`
-  // for **isSorted** to use binary search.
-  _.indexOf = function(array, item, isSorted) {
-    var i = 0, length = array && array.length;
-    if (typeof isSorted == 'number') {
-      i = isSorted < 0 ? Math.max(0, length + isSorted) : isSorted;
-    } else if (isSorted && length) {
-      i = _.sortedIndex(array, item);
-      return array[i] === item ? i : -1;
-    }
-    if (item !== item) {
-      var index = _.findIndex(slice.call(array, i), _.isNaN);
-      return index >= 0 ? index + i : -1;
-    }
-    for (; i < length; i++) if (array[i] === item) return i;
-    return -1;
-  };
-
-  _.lastIndexOf = function(array, item, from) {
-    var idx = array ? array.length : 0;
-    if (typeof from == 'number') {
-      idx = from < 0 ? idx + from + 1 : Math.min(idx, from + 1);
-    }
-    if (item !== item) {
-      return _.findLastIndex(slice.call(array, 0, idx), _.isNaN);
-    }
-    while (--idx >= 0) if (array[idx] === item) return idx;
-    return -1;
-  };
-
   // Generator function to create the findIndex and findLastIndex functions
-  function createIndexFinder(dir) {
+  function createPredicateIndexFinder(dir) {
     return function(array, predicate, context) {
       predicate = cb(predicate, context);
       var length = array != null && array.length;
@@ -649,9 +617,8 @@
   }
 
   // Returns the first index on an array-like that passes a predicate test
-  _.findIndex = createIndexFinder(1);
-
-  _.findLastIndex = createIndexFinder(-1);
+  _.findIndex = createPredicateIndexFinder(1);
+  _.findLastIndex = createPredicateIndexFinder(-1);
 
   // Use a comparator function to figure out the smallest index at which
   // an object should be inserted so as to maintain order. Uses binary search.
@@ -666,6 +633,38 @@
     return low;
   };
 
+  // Generator function to create the indexOf and lastIndexOf functions
+  function createIndexFinder(dir, predicateFind, sortedIndex) {
+    return function(array, item, idx) {
+      var i = 0, length = array ? array.length : -1;
+      if (typeof idx == 'number') {
+        if (dir > 0) {
+            i = idx >= 0 ? idx : Math.max(idx + length, i);
+        } else {
+            length = idx >= 0 ? Math.min(idx + 1, length) : idx + length + 1;
+        }
+      } else if (sortedIndex && idx && length) {
+        idx = _[sortedIndex](array, item);
+        return array[idx] === item ? idx : -1;
+      }
+      if (item !== item) {
+        idx = _[predicateFind](slice.call(array, i, length), _.isNaN);
+        return idx >= 0 ? idx + i : -1;
+      }
+      for (idx = dir > 0 ? i : length - 1; idx >= 0 && idx < length; idx += dir) {
+        if (array[idx] === item) return idx;
+      }
+      return -1;
+    };
+  }
+
+  // Return the position of the first occurrence of an item in an array,
+  // or -1 if the item is not included in the array.
+  // If the array is large and already in sort order, pass `true`
+  // for **isSorted** to use binary search.
+  _.indexOf = createIndexFinder(1, 'findIndex', 'sortedIndex');
+  _.lastIndexOf = createIndexFinder(-1, 'findLastIndex');
+
   // Generate an integer Array containing an arithmetic progression. A port of
   // the native Python `range()` function. See
   // [the Python documentation](http://docs.python.org/library/functions.html#range).