Before scripts - Postchi

Before scripts run immediately before Postchi sends a request. You receive the request object and can mutate it freely — whatever state it’s in when the script finishes is what gets sent.

File naming

Place a file named <request-name>.before.js in the same folder as your request file:

requests/
  auth/
    login.chttp
    login.before.js   ← runs before login.chttp

For a script that applies to every request in a folder, create before.js in that folder:

requests/
  auth/
    before.js         ← runs before every request in auth/ and subfolders
    login.chttp
    refresh.chttp

The folder-level before.js runs first, then the request-level <name>.before.js. This means the request-level script always sees changes made by the folder-level script.

Available context

Postchi injects these variables into every before script:

Variable	Type	Description
`request`	object	The request about to be sent. Mutating this object changes what Postchi sends.
`env`	object	All active environment variables as string key-value pairs. Read-only.
`fetch`	function	The global `fetch` function.

The `request` object

Property	Type	Description
`request.method`	string	HTTP method, e.g. `"GET"`
`request.url`	string	Full URL including any template variables already resolved
`request.headers`	object	Headers as `{ name: value }` pairs
`request.body`	string \| null	Request body as a string, or `null`

Examples

Add a dynamic header

// Add a timestamp to every request
request.headers['X-Request-Time'] = new Date().toISOString();

Build the URL from environment variables

// Append a version query parameter from the environment
const version = env.api_version || 'v1';
request.url = request.url + '?version=' + version;

Modify a JSON body

// Add a nonce to the request body before sending
const body = JSON.parse(request.body);
body.nonce = Math.random().toString(36).slice(2);
request.body = JSON.stringify(body);

Add a Bearer token from the environment

request.headers['Authorization'] = 'Bearer ' + env.api_token;

Notes

Before scripts cannot cancel a request — they can only transform it. If your script throws an error, Postchi surfaces the error and does not send the request.

Put shared authentication logic in a folder-level before.js so you only write it once and it applies to every request in that folder automatically.

​File naming

​Available context

​The request object

​Examples

​Add a dynamic header

​Build the URL from environment variables

​Modify a JSON body

​Add a Bearer token from the environment

​Notes

File naming

Available context

The `request` object

Examples

Add a dynamic header

Build the URL from environment variables

Modify a JSON body

Add a Bearer token from the environment

Notes