Make _.xyzBy methods provide just a single param to their callbacks.

lodash.js

@@ -2339,8 +2339,8 @@
      */
     function basePickBy(object, predicate) {
       var result = {};
-      baseForIn(object, function(value, key, object) {
+      baseForIn(object, function(value, key) {
-        if (predicate(value, key, object)) {
+        if (predicate(value)) {
           result[key] = value;
         }
       });
@@ -2576,12 +2576,12 @@
           index = -1;
 
       iteratees = arrayMap(iteratees.length ? iteratees : Array(1), function(iteratee) {
-        return toIteratee(iteratee, 3);
+        return toIteratee(iteratee, 1);
       });
 
       var result = baseMap(collection, function(value, key, collection) {
         var criteria = arrayMap(iteratees, function(iteratee) {
-          return iteratee(value, key, collection);
+          return iteratee(value);
         });
         return { 'criteria': criteria, 'index': ++index, 'value': value };
       });
@@ -3029,11 +3029,11 @@
 
           while (++index < length) {
             var value = collection[index];
-            setter(result, value, iteratee(value, index, collection), collection);
+            setter(result, value, iteratee(value), collection);
           }
         } else {
           baseEach(collection, function(value, key, collection) {
-            setter(result, value, iteratee(value, key, collection), collection);
+            setter(result, value, iteratee(value), collection);
           });
         }
         return result;
@@ -5892,7 +5892,7 @@
      * Creates an object composed of keys generated from the results of running
      * each element of `collection` through `iteratee`. The corresponding value
      * of each key is the number of times the key was returned by `iteratee`.
-     * The iteratee is invoked with three arguments: (value, index|key, collection).
+     * The iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
@@ -6128,7 +6128,7 @@
      * Creates an object composed of keys generated from the results of running
      * each element of `collection` through `iteratee`. The corresponding value
      * of each key is an array of the elements responsible for generating the key.
-     * The iteratee is invoked with three arguments: (value, index|key, collection).
+     * The iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
@@ -6201,7 +6201,7 @@
      * Creates an object composed of keys generated from the results of running
      * each element of `collection` through `iteratee`. The corresponding value
      * of each key is the last element responsible for generating the key. The
-     * iteratee is invoked with three arguments: (value, index|key, collection).
+     * iteratee is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
@@ -6596,8 +6596,7 @@
      * Creates an array of elements, sorted in ascending order by the results of
      * running each element in a collection through each iteratee. This method
      * performs a stable sort, that is, it preserves the original sort order of
-     * equal elements. The iteratees are invoked with three arguments:
+     * equal elements. The iteratees are invoked with one argument: (value).
-     * (value, index|key, collection).
      *
      * @static
      * @memberOf _
@@ -9425,9 +9424,9 @@
      * // => { 'user': 'fred' }
      */
     function omitBy(object, predicate) {
-      predicate = getIteratee(predicate, 3);
+      predicate = getIteratee(predicate);
-      return basePickBy(object, function(value, key, object) {
+      return basePickBy(object, function(value) {
-        return !predicate(value, key, object);
+        return !predicate(value);
       });
     }
 
@@ -9475,7 +9474,7 @@
 
     /**
      * Creates an object composed of the `object` properties `predicate` returns
-     * truthy for. The predicate is invoked with three arguments: (value, key, object).
+     * truthy for. The predicate is invoked with one argument: (value).
      *
      * @static
      * @memberOf _
@@ -9491,7 +9490,7 @@
      * // => { 'user': 'fred' }
      */
     function pickBy(object, predicate) {
-      return object == null ? {} : basePickBy(object, getIteratee(predicate, 3));
+      return object == null ? {} : basePickBy(object, getIteratee(predicate));
     }
 
     /**

test/test.js

@@ -4747,7 +4747,7 @@
     _.each(methods, function(methodName) {
       var array = [1, 2, 3],
           func = _[methodName],
-          isExtremum = /^(?:max|min)/.test(methodName),
+          isBy = /(^partition|By)$/.test(methodName),
           isFind = /^find/.test(methodName),
           isSome = methodName == 'some';
 
@@ -4767,7 +4767,7 @@
           if (_.includes(objectMethods, methodName)) {
             expected[1] += '';
           }
-          if (isExtremum) {
+          if (isBy) {
             expected.length = 1;
           }
           deepEqual(args, expected);
@@ -4784,12 +4784,12 @@
 
           var expected = [[1, 0, array], [undefined, 1, array], [3, 2, array]];
 
-          if (isExtremum) {
+          if (isBy) {
             expected = _.map(expected, function(args) {
               return args.slice(0, 1);
             });
           }
-          if (_.includes(objectMethods, methodName)) {
+          else if (_.includes(objectMethods, methodName)) {
             expected = _.map(expected, function(args) {
               args[1] += '';
               return args;
@@ -4888,9 +4888,9 @@
         Foo.prototype.b = 2;
 
         if (func) {
-          var keys = [];
+          var values = [];
-          func(new Foo, function(value, key) { keys.push(key); });
+          func(new Foo, function(value) { values.push(value); });
-          deepEqual(keys, ['a']);
+          deepEqual(values, [1]);
         }
         else {
           skipTest();
@@ -11204,29 +11204,33 @@
   _.each(['omit', 'omitBy'], function(methodName) {
     var expected = { 'b': 2, 'd': 4 },
         func = _[methodName],
-        object = { 'a': 1, 'b': 2, 'c': 3, 'd': 4 };
+        object = { 'a': 1, 'b': 2, 'c': 3, 'd': 4 },
+        prop = function(object, props) { return props; };
 
-    var prop = methodName == 'omit' ? _.identity : function(props) {
+    if (methodName == 'omitBy') {
-      props = typeof props == 'string' ? [props] : props;
+      prop = function(object, props) {
-      return function(value, key) {
+        props = typeof props == 'string' ? [props] : props;
-        return _.includes(props, key);
+        return function(value) {
+          return _.some(props, function(key) { return object[key] === value; });
+        };
       };
-    };
+    }
-
     test('`_.' + methodName + '` should create an object with omitted properties', 2, function() {
-      deepEqual(func(object, prop('a')), { 'b': 2, 'c': 3, 'd': 4 });
+      deepEqual(func(object, prop(object, 'a')), { 'b': 2, 'c': 3, 'd': 4 });
-      deepEqual(func(object, prop(['a', 'c'])), expected);
+      deepEqual(func(object, prop(object, ['a', 'c'])), expected);
     });
 
     test('`_.' + methodName + '` should iterate over inherited properties', 1, function() {
       function Foo() {}
       Foo.prototype = object;
 
-      deepEqual(func(new Foo, prop(['a', 'c'])), expected);
+      var foo = new Foo;
+      deepEqual(func(foo, prop(object, ['a', 'c'])), expected);
     });
 
     test('`_.' + methodName + '` should work with an array `object` argument', 1, function() {
-      deepEqual(func([1, 2, 3], prop(['0', '2'])), { '1': 2 });
+      var array = [1, 2, 3];
+      deepEqual(func(array, prop(array, ['0', '2'])), { '1': 2 });
     });
   });
 
@@ -11921,29 +11925,33 @@
   _.each(['pick', 'pickBy'], function(methodName) {
     var expected = { 'a': 1, 'c': 3 },
         func = _[methodName],
-        object = { 'a': 1, 'b': 2, 'c': 3, 'd': 4 };
+        object = { 'a': 1, 'b': 2, 'c': 3, 'd': 4 },
+        prop = function(object, props) { return props; };
 
-    var prop = methodName == 'pick' ? _.identity : function(props) {
+    if (methodName == 'pickBy') {
-      props = typeof props == 'string' ? [props] : props;
+      prop = function(object, props) {
-      return function(value, key) {
+        props = typeof props == 'string' ? [props] : props;
-        return _.includes(props, key);
+        return function(value) {
+          return _.some(props, function(key) { return object[key] === value; });
+        };
       };
-    };
+    }
-
     test('`_.' + methodName + '` should create an object of picked properties', 2, function() {
-      deepEqual(func(object, prop('a')), { 'a': 1 });
+      deepEqual(func(object, prop(object, 'a')), { 'a': 1 });
-      deepEqual(func(object, prop(['a', 'c'])), expected);
+      deepEqual(func(object, prop(object, ['a', 'c'])), expected);
     });
 
     test('`_.' + methodName + '` should iterate over inherited properties', 1, function() {
       function Foo() {}
       Foo.prototype = object;
 
-      deepEqual(func(new Foo, prop(['a', 'c'])), expected);
+      var foo = new Foo;
+      deepEqual(func(foo, prop(foo, ['a', 'c'])), expected);
     });
 
     test('`_.' + methodName + '` should work with an array `object` argument', 1, function() {
-      deepEqual(func([1, 2, 3], prop('1')), { '1': 2 });
+      var array = [1, 2, 3];
+      deepEqual(func(array, prop(array, '1')), { '1': 2 });
     });
   });