feat: add IsSortedByKey

slice/slice.go

@@ -860,6 +860,34 @@ func IsSorted[T constraints.Ordered](slice []T) bool {
 	return IsAscending(slice) || IsDescending(slice)
 }
 
+// IsSortedByKey checks if a slice is sorted by iteratee function.
+// Play: todo
+func IsSortedByKey[T any, K constraints.Ordered](slice []T, iteratee func(item T) K) bool {
+	size := len(slice)
+
+	isAscending := func(data []T) bool {
+		for i := 0; i < size-1; i++ {
+			if iteratee(data[i]) > iteratee(data[i+1]) {
+				return false
+			}
+		}
+
+		return true
+	}
+
+	isDescending := func(data []T) bool {
+		for i := 0; i < size-1; i++ {
+			if iteratee(data[i]) < iteratee(data[i+1]) {
+				return false
+			}
+		}
+
+		return true
+	}
+
+	return isAscending(slice) || isDescending(slice)
+}
+
 // Sort sorts a slice of any ordered type(number or string), use quick sort algrithm.
 // default sort order is ascending (asc), if want descending order, set param `sortOrder` to `desc`.
 // Play: https://go.dev/play/p/V9AVjzf_4Fk

slice/slice_example_test.go

@@ -733,6 +733,27 @@ func ExampleIsSorted() {
 	// false
 }
 
+func ExampleIsSortedByKey() {
+	result1 := IsSortedByKey([]string{"a", "ab", "abc"}, func(s string) int {
+		return len(s)
+	})
+	result2 := IsSortedByKey([]string{"abc", "ab", "a"}, func(s string) int {
+		return len(s)
+	})
+	result3 := IsSortedByKey([]string{"abc", "a", "ab"}, func(s string) int {
+		return len(s)
+	})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// true
+	// true
+	// false
+}
+
 func ExampleSort() {
 	nums := []int{1, 4, 3, 2, 5}
 

slice/slice_test.go

@@ -627,6 +627,22 @@ func TestIsSorted(t *testing.T) {
 	assert.Equal(false, IsSorted([]int{2, 1, 3, 4, 5}))
 }
 
+func TestIsSortedByKey(t *testing.T) {
+	assert := internal.NewAssert(t, "TestIsSortedByKey")
+
+	assert.Equal(true, IsSortedByKey([]string{"a", "ab", "abc"}, func(s string) int {
+		return len(s)
+	}))
+
+	assert.Equal(true, IsSortedByKey([]string{"abc", "ab", "a"}, func(s string) int {
+		return len(s)
+	}))
+
+	assert.Equal(false, IsSortedByKey([]string{"abc", "a", "ab"}, func(s string) int {
+		return len(s)
+	}))
+}
+
 func TestSort(t *testing.T) {
 	assert := internal.NewAssert(t, "TestSort")