chore: add support for TypeScript code splitting (#11160)

- **Description:** Adds typescript language to `TextSplitter`

---------

Co-authored-by: Jacob Lee <jacoblee93@gmail.com>

libs/langchain/langchain/text_splitter.py

@@ -615,6 +615,7 @@ class Language(str, Enum):
     GO = "go"
     JAVA = "java"
     JS = "js"
+    TS = "ts"
     PHP = "php"
     PROTO = "proto"
     PYTHON = "python"
@@ -782,6 +783,32 @@ class RecursiveCharacterTextSplitter(TextSplitter):
                 " ",
                 "",
             ]
+        elif language == Language.TS:
+            return [
+                "\nenum ",
+                "\ninterface ",
+                "\nnamespace ",
+                "\ntype ",
+                # Split along class definitions
+                "\nclass ",
+                # Split along function definitions
+                "\nfunction ",
+                "\nconst ",
+                "\nlet ",
+                "\nvar ",
+                # Split along control flow statements
+                "\nif ",
+                "\nfor ",
+                "\nwhile ",
+                "\nswitch ",
+                "\ncase ",
+                "\ndefault ",
+                # Split by the normal type of lines
+                "\n\n",
+                "\n",
+                " ",
+                "",
+            ]
         elif language == Language.PHP:
             return [
                 # Split along function definitions

libs/langchain/tests/unit_tests/test_text_splitter.py

@@ -472,6 +472,33 @@ helloWorld();
     ]
 
 
+def test_typescript_code_splitter() -> None:
+    splitter = RecursiveCharacterTextSplitter.from_language(
+        Language.TS, chunk_size=CHUNK_SIZE, chunk_overlap=0
+    )
+    code = """
+function helloWorld(): void {
+  console.log("Hello, World!");
+}
+
+// Call the function
+helloWorld();
+    """
+    chunks = splitter.split_text(code)
+    assert chunks == [
+        "function",
+        "helloWorld():",
+        "void {",
+        'console.log("He',
+        "llo,",
+        'World!");',
+        "}",
+        "// Call the",
+        "function",
+        "helloWorld();",
+    ]
+
+
 def test_java_code_splitter() -> None:
     splitter = RecursiveCharacterTextSplitter.from_language(
         Language.JAVA, chunk_size=CHUNK_SIZE, chunk_overlap=0