Ensure _.first, _.last, and _.sample return the undefined if called with a falsey argument or an empty array if called with a falsey argument and an n value.

lodash.js

@@ -4320,9 +4320,8 @@
      * // => [{ 'name': 'apple', 'type': 'fruit' }, { 'name': 'banana', 'type': 'fruit' }]
      */
     function first(array, callback, thisArg) {
-      if (array) {
       var n = 0,
-            length = array.length;
+          length = array ? array.length : 0;
 
       if (typeof callback != 'number' && callback != null) {
         var index = -1;
@@ -4333,12 +4332,11 @@
       } else {
         n = callback;
         if (n == null || thisArg) {
-            return array[0];
+          return array ? array[0] : undefined;
         }
       }
       return slice(array, 0, nativeMin(nativeMax(0, n), length));
     }
-    }
 
     /**
      * Flattens a nested array (the nesting can be to any depth). If `isShallow`
@@ -4485,11 +4483,8 @@
      * // => [{ 'name': 'banana', 'type': 'fruit' }]
      */
     function initial(array, callback, thisArg) {
-      if (!array) {
-        return [];
-      }
       var n = 0,
-          length = array.length;
+          length = array ? array.length : 0;
 
       if (typeof callback != 'number' && callback != null) {
         var index = length;
@@ -4618,9 +4613,8 @@
      * // => [{ 'name': 'beet', 'type': 'vegetable' }, { 'name': 'carrot', 'type': 'vegetable' }]
      */
     function last(array, callback, thisArg) {
-      if (array) {
       var n = 0,
-            length = array.length;
+          length = array ? array.length : 0;
 
       if (typeof callback != 'number' && callback != null) {
         var index = length;
@@ -4631,12 +4625,11 @@
       } else {
         n = callback;
         if (n == null || thisArg) {
-            return array[length - 1];
+          return array ? array[length - 1] : undefined;
         }
       }
       return slice(array, nativeMax(0, length - n));
     }
-    }
 
     /**
      * Gets the index at which the last occurrence of `value` is found using strict

test/test.js

@@ -4380,7 +4380,7 @@
     ];
 
     _.forEach(funcs, function(methodName) {
-      test('`_.' + methodName + '` should return an unwrapped value', function() {
+      test('`_(...).' + methodName + '` should return an unwrapped value', function() {
         var result = methodName == 'reduceRight'
           ? wrapped[methodName](_.identity)
           : wrapped[methodName]();
@@ -4400,17 +4400,46 @@
 
     var funcs = [
       'first',
-      'last'
+      'last',
+      'sample'
     ];
 
     _.forEach(funcs, function(methodName) {
-      test('`_.' + methodName + '` should return an unwrapped value', function() {
+      test('`_(...).' + methodName + '` called without an `n` argument should return an unwrapped value', function() {
         equal(typeof wrapped[methodName](), 'number');
       });
 
-      test('`_.' + methodName + '` should return a wrapped value', function() {
+      test('`_(...).' + methodName + '` called with an `n` argument should return a wrapped value', function() {
         ok(wrapped[methodName](1) instanceof _);
       });
+
+      test('`_.' + methodName + '` should return `undefined` when querying falsey arguments without an `n` argument', function() {
+        var actual = [],
+            expected = _.map(falsey, function() { return undefined; }),
+            func = _[methodName];
+
+        _.forEach(falsey, function(value, index) {
+          try {
+            actual.push(index ? func(value) : func());
+          } catch(e) { console.log(e)}
+        });
+
+        deepEqual(actual, expected);
+      });
+
+      test('`_.' + methodName + '` should return an empty array when querying falsey arguments with an `n` argument', function() {
+        var actual = [],
+            expected = _.map(falsey, function() { return []; }),
+            func = _[methodName];
+
+        _.forEach(falsey, function(value, index) {
+          try {
+            actual.push(func(value, 2));
+          } catch(e) { }
+        });
+
+        deepEqual(actual, expected);
+      });
     });
   }());