feat: add JoinFunc

docs/api/packages/slice.md

@@ -106,6 +106,8 @@ import (
 -   [RightPadding](#RightPadding)
 -   [LeftPadding](#LeftPadding)
 -   [Frequency](#Frequency)
+-   [JoinFunc](#JoinFunc)
+
 
 <div STYLE="page-break-after: always;"></div>
 
@@ -2984,4 +2986,34 @@ func main() {
     // Output:
     // map[a:1 b:2 c:3]
 }
+```
+
+### <span id="JoinFunc">JoinFunc</span>
+
+<p>将切片元素用给定的分隔符连接成一个单一的字符串。</p>
+
+<b>函数签名:</b>
+
+```go
+func JoinFunc[T any](slice []T, sep string, transform func(T) T) string
+```
+
+<b>示例:<span style="float:right;display:inline-block;">[运行](todo)</span></b>
+
+```go
+import (
+    "fmt"
+    "github.com/duke-git/lancet/v2/slice"
+)
+
+func main() {
+    result := slice.JoinFunc([]string{"a", "b", "c"}, ", ", func(s string) string {
+        return strings.ToUpper(s)
+    })
+
+    fmt.Println(result)
+
+    // Output:
+    // A, B, C
+}
 ```

docs/en/api/packages/slice.md

@@ -2979,4 +2979,34 @@ func main() {
     // Output:
     // map[a:1 b:2 c:3]
 }
+```
+
+### <span id="JoinFunc">JoinFunc</span>
+
+<p>Joins the slice elements into a single string with the given separator.</p>
+
+<b>Signature:</b>
+
+```go
+func JoinFunc[T any](slice []T, sep string, transform func(T) T) string
+```
+
+<b>Example:<span style="float:right;display:inline-block;">[Run](todo)</span></b>
+
+```go
+import (
+    "fmt"
+    "github.com/duke-git/lancet/v2/slice"
+)
+
+func main() {
+    result := slice.JoinFunc([]string{"a", "b", "c"}, ", ", func(s string) string {
+        return strings.ToUpper(s)
+    })
+
+    fmt.Println(result)
+
+    // Output:
+    // A, B, C
+}
 ```

slice/slice.go

@@ -1398,3 +1398,16 @@ func Frequency[T comparable](slice []T) map[T]int {
 
 	return result
 }
+
+// JoinFunc joins the slice elements into a single string with the given separator.
+// Play: todo
+func JoinFunc[T any](slice []T, sep string, transform func(T) T) string {
+	var buf strings.Builder
+	for i, v := range slice {
+		if i > 0 {
+			buf.WriteString(sep)
+		}
+		buf.WriteString(fmt.Sprint(transform(v)))
+	}
+	return buf.String()
+}

slice/slice_example_test.go

@@ -1261,3 +1261,14 @@ func ExampleFrequency() {
 	// Output:
 	// map[a:1 b:2 c:3]
 }
+
+func ExampleJoinFunc() {
+	result := JoinFunc([]string{"a", "b", "c"}, ", ", func(s string) string {
+		return strings.ToUpper(s)
+	})
+
+	fmt.Println(result)
+
+	// Output:
+	// A, B, C
+}

slice/slice_test.go

@@ -1816,3 +1816,43 @@ func TestFrequency(t *testing.T) {
 		assert.Equal(expected, result)
 	})
 }
+
+func TestJoinFunc(t *testing.T) {
+	t.Parallel()
+
+	assert := internal.NewAssert(t, "TestJoinFunc")
+
+	t.Run("basic case", func(t *testing.T) {
+		result := JoinFunc([]int{1, 2, 3}, ", ", func(i int) int {
+			return i * 2
+		})
+
+		expected := "2, 4, 6"
+		assert.Equal(expected, result)
+	})
+
+	t.Run("empty slice", func(t *testing.T) {
+		result := JoinFunc([]int{}, ", ", func(i int) int {
+			return i * 2
+		})
+
+		assert.Equal("", result)
+	})
+
+	t.Run("single element slice", func(t *testing.T) {
+		result := JoinFunc([]int{1}, ", ", func(i int) int {
+			return i * 2
+		})
+
+		assert.Equal("2", result)
+	})
+
+	t.Run("string slice", func(t *testing.T) {
+		result := JoinFunc([]string{"a", "b", "c"}, ", ", func(s string) string {
+			return strings.ToUpper(s)
+		})
+
+		expected := "A, B, C"
+		assert.Equal(expected, result)
+	})
+}