truncate tool and testCases; then autoupdated index file

src/pages/list/truncate/service.ts

@@ -0,0 +1,30 @@
+export type SplitOperatorType = 'symbol' | 'regex';
+
+export function truncateList(
+    splitOperatorType: SplitOperatorType,
+    input: string,
+    splitSeparator: string,
+    joinSeparator: string,
+    end: boolean,
+    length?: number,
+): string {
+    let array: string[];
+    let truncatedArray: string[];
+    switch (splitOperatorType) {
+        case 'symbol':
+            array = input.split(splitSeparator);
+            break;
+        case 'regex':
+            array = input.split(new RegExp(splitSeparator));
+            break;
+    }
+    if (length !== undefined) {
+        if (length < 0) {
+            throw new Error("Length value must be a positive number.")
+        }
+        truncatedArray = end ? array.slice(0, length) : array.slice(array.length - length, array.length);
+        return truncatedArray.join(joinSeparator);
+    }
+    throw new Error("Length value isn't a value number.");
+
+}