feat: Implement funk.Nth

nth.go

@@ -0,0 +1,28 @@
+package funk
+
+import (
+	"reflect"
+)
+
+// Nth returns the element at the specified index from the array (Slice).
+// The index is 1-based, so the first element is at index 1.
+func Nth(in interface{}, number int) interface{} {
+	if !IsCollection(in) {
+		panic("First parameter must be a collection")
+	}
+
+	inValue := reflect.ValueOf(in)
+
+	if number >= inValue.Len() {
+		return nil
+	}
+
+	if number < 0 {
+		if number+inValue.Len() < 0 {
+			return nil
+		}
+		number = number + inValue.Len()
+	}
+
+	return inValue.Index(number).Interface()
+}

nth_test.go

@@ -0,0 +1,61 @@
+package funk
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_nth_valid_n_great_than_array_length(t *testing.T) {
+	result := Nth([]int{1, 2, 3}, 4)
+
+	assert.Equal(t, nil, result)
+}
+
+func Test_nth_valid_n_less_than_zero_one(t *testing.T) {
+	result := Nth([]int32{1, 2, 3}, -3)
+
+	assert.Equal(t, int32(1), result)
+}
+
+func Test_nth_valid_n_less_than_zero_two(t *testing.T) {
+	result := Nth([]int32{1, 2, 3}, -4)
+
+	assert.Equal(t, nil, result)
+}
+
+func Test_nth_valid_int64(t *testing.T) {
+	result := Nth([]int64{1, 2, 3}, 2)
+
+	assert.Equal(t, int64(3), result)
+}
+
+func Test_nth_valid_float32(t *testing.T) {
+	result := Nth([]float32{1, 2, 3}, 1)
+
+	assert.Equal(t, float32(2), result)
+}
+
+func Test_nth_valid_float64(t *testing.T) {
+	result := Nth([]float64{1.1, 2.2, 3.3}, 2)
+
+	assert.Equal(t, 3.3, result)
+}
+
+func Test_nth_valid_bool(t *testing.T) {
+	result := Nth([]bool{true, true, true, false, true}, 2)
+
+	assert.Equal(t, true, result)
+}
+
+func Test_nth_valid_string(t *testing.T) {
+	result := Nth([]string{"a", "b", "c", "d"}, -2)
+
+	assert.Equal(t, "c", result)
+}
+
+func Test_nth_valid_interface(t *testing.T) {
+	result := Nth([]interface{}{"1.1", true, 2.2, float32(3.3)}, 2)
+
+	assert.Equal(t, 2.2, result)
+}