Add baseWhile and createBaseEach.

lodash.src.js

@@ -2025,21 +2025,7 @@
      * @param {Function} iteratee The function invoked per iteration.
      * @returns {Array|Object|string} Returns `collection`.
      */
-    function baseEach(collection, iteratee) {
+    var baseEach = createBaseEach(baseForOwn);
-      var length = collection ? collection.length : 0;
-      if (!isLength(length)) {
-        return baseForOwn(collection, iteratee);
-      }
-      var index = -1,
-          iterable = toObject(collection);
-
-      while (++index < length) {
-        if (iteratee(iterable[index], index, iterable) === false) {
-          break;
-        }
-      }
-      return collection;
-    }
 
     /**
      * The base implementation of `_.forEachRight` without support for callback
@@ -2050,19 +2036,7 @@
      * @param {Function} iteratee The function invoked per iteration.
      * @returns {Array|Object|string} Returns `collection`.
      */
-    function baseEachRight(collection, iteratee) {
+    var baseEachRight = createBaseEach(baseForOwnRight, true);
-      var length = collection ? collection.length : 0;
-      if (!isLength(length)) {
-        return baseForOwnRight(collection, iteratee);
-      }
-      var iterable = toObject(collection);
-      while (length--) {
-        if (iteratee(iterable[length], length, iterable) === false) {
-          break;
-        }
-      }
-      return collection;
-    }
 
     /**
      * The base implementation of `_.every` without support for callback
@@ -2858,6 +2832,27 @@
       return result;
     }
 
+    /**
+     * The base implementation of `_.dropRightWhile`, `_.dropWhile`, `_.takeRightWhile`,
+     * and `_.takeWhile` without support for callback shorthands and `this` binding.
+     *
+     * @private
+     * @param {Array} array The array to query.
+     * @param {Function} predicate The function invoked per iteration.
+     * @param {boolean} [isDrop] Specify dropping elements instead of taking them.
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Array} Returns the slice of `array`.
+     */
+    function baseWhile(array, predicate, isDrop, fromRight) {
+      var length = array.length,
+          index = fromRight ? length : -1;
+
+      while ((fromRight ? index-- : ++index < length) && predicate(array[index], index, array)) {}
+      return isDrop
+        ? baseSlice(array, (fromRight ? 0 : index), (fromRight ? index + 1 : length))
+        : baseSlice(array, (fromRight ? index + 1 : 0), (fromRight ? length : index));
+    }
+
     /**
      * The base implementation of `wrapperValue` which returns the result of
      * performing a sequence of actions on the unwrapped `value`, where each
@@ -3095,7 +3090,6 @@
      * **Note:** This function is used to create `_.countBy`, `_.groupBy`, `_.indexBy`,
      * and `_.partition`.
      *
-     *
      * @private
      * @param {Function} setter The function to set keys and values of the accumulator object.
      * @param {Function} [initializer] The function to initialize the accumulator object.
@@ -3168,6 +3162,32 @@
       };
     }
 
+    /**
+     * Creates a `baseEach` or `baseEachRight` function.
+     *
+     * @private
+     * @param {Function} eachFunc The function to iterate over a collection.
+     * @param {boolean} [fromRight] Specify iterating from right to left.
+     * @returns {Function} Returns the new base function.
+     */
+    function createBaseEach(eachFunc, fromRight) {
+      return function(collection, iteratee) {
+        var length = collection ? collection.length : 0;
+        if (!isLength(length)) {
+          return eachFunc(collection, iteratee);
+        }
+        var index = fromRight ? length : -1,
+            iterable = toObject(collection);
+
+        while ((fromRight ? index-- : ++index < length)) {
+          if (iteratee(iterable[index], index, iterable) === false) {
+            break;
+          }
+        }
+        return collection;
+      };
+    }
+
     /**
      * Creates a base function for `_.forIn` or `_.forInRight`.
      *
@@ -4680,13 +4700,9 @@
      * // => ['barney', 'fred', 'pebbles']
      */
     function dropRightWhile(array, predicate, thisArg) {
-      var length = array ? array.length : 0;
+      return (array && array.length)
-      if (!length) {
+        ? baseWhile(array, getCallback(predicate, thisArg, 3), true, true)
-        return [];
+        : [];
-      }
-      predicate = getCallback(predicate, thisArg, 3);
-      while (length-- && predicate(array[length], length, array)) {}
-      return baseSlice(array, 0, length + 1);
     }
 
     /**
@@ -4739,14 +4755,9 @@
      * // => ['barney', 'fred', 'pebbles']
      */
     function dropWhile(array, predicate, thisArg) {
-      var length = array ? array.length : 0;
+      return (array && array.length)
-      if (!length) {
+        ? baseWhile(array, getCallback(predicate, thisArg, 3), true)
-        return [];
+        : [];
-      }
-      var index = -1;
-      predicate = getCallback(predicate, thisArg, 3);
-      while (++index < length && predicate(array[index], index, array)) {}
-      return baseSlice(array, index);
     }
 
     /**
@@ -5536,13 +5547,9 @@
      * // => []
      */
     function takeRightWhile(array, predicate, thisArg) {
-      var length = array ? array.length : 0;
+      return (array && array.length)
-      if (!length) {
+        ? baseWhile(array, getCallback(predicate, thisArg, 3), false, true)
-        return [];
+        : [];
-      }
-      predicate = getCallback(predicate, thisArg, 3);
-      while (length-- && predicate(array[length], length, array)) {}
-      return baseSlice(array, length + 1);
     }
 
     /**
@@ -5595,14 +5602,9 @@
      * // => []
      */
     function takeWhile(array, predicate, thisArg) {
-      var length = array ? array.length : 0;
+      return (array && array.length)
-      if (!length) {
+        ? baseWhile(array, getCallback(predicate, thisArg, 3))
-        return [];
+        : [];
-      }
-      var index = -1;
-      predicate = getCallback(predicate, thisArg, 3);
-      while (++index < length && predicate(array[index], index, array)) {}
-      return baseSlice(array, 0, index);
     }
 
     /**