***

title: Route response data with TypeScript in Flows
updated: 2025-09-20T00:00:00.000Z
slug: docs/postman-flows/typescript/typescript-health-performance-routing
max-toc-depth: 2
----------------

This example uses three TypeScript expressions to route response data based on health and performance using a **Condition** block. The first expression to return `true` routes the response data through its output port. If none of the three TypeScript expressions resolve to true, the **Condition** block routes the response data through the **Default** output port.

## Example JSON

The example uses JSON data from a GET request to `postman-echo.com` like this:

```json
{
  "body": {
    "args": {},
    "headers": {
      "host": "postman-echo.com",
      "x-request-start": "t1757972551.591",
      "connection": "close",
      "x-forwarded-proto": "https",
      "x-forwarded-port": "443",
      "x-amzn-trace-id": "Root=1-68c88847-aaaaaaaaaaaaaaaaaaaaaaaa",
      "user-agent": "PostmanRuntime/7.46.0",
      "accept": "*/*",
      "cache-control": "no-cache",
      "postman-token": "00000000-1111-2222-3333-444444444444",
      "accept-encoding": "gzip, deflate, br",
      "cookie": "sails.sid=s%3AdummySessionId1234567890.abcdef1234567890"
    },
    "url": "https://postman-echo.com/get"
  },
  "http": {
    "status": 200,
    "headers": {
      "Date": "Mon, 15 Sep 2025 21:42:31 GMT",
      "Content-Type": "application/json; charset=utf-8",
      "Content-Length": "621",
      "Connection": "keep-alive",
      "Server": "nginx",
      "ETag": "W/"26d-FAKEETAG1234567890"",
      "Set-Cookie": "sails.sid=s%3AdummySetCookieId0987654321.qwerty9876543210; Path=/; HttpOnly"
    }
  },
  "tests": [],
  "binary": false
}
```

## Condition 1: Check for critical server errors

The TypeScript in this condition finds the response's status code and checks if the code is greater than or equal to 400:

```javascript
response.http.status >= 400
```

## Condition 2: Check for slow response

The TypeScript in this condition finds the `Server-Timing` header value and checks if it's greater than 1000. The `Server-Timing` header shows the number of milliseconds the request took to process. If it's greater than 1000 ms, that could indicate a slow response.

```javascript
Number((response.http.headers["Server-Timing"] || "")
  .match(/dur=([\d.]+)/)?.[1]) > 1000
```

## Condition 3: Not JSON

The TypeScript in this condition checks if the `Content-Type` header is missing the string `application/json`. If `application/json` isn't present in the header, the expression returns true and routes the response from this condition's output port. If the string is present, the expression returns false.

```javascript
!(response.http.headers["Content-Type"]?.includes("application/json"))
```

## Example

To see this TypeScript in an example flow, check out [TypeScript example 3: Response health and performance routing](https://www.postman.com/postman/flows-snippets/flow/68c9cb22d0954f00138d7ea9).