Scripting API

LiteClient supports pre-request and post-response scripts using a Postman-compatible pm API. Write JavaScript code that runs before sending a request or after receiving a response to automate workflows, set variables dynamically, and validate responses.

Overview

Scripts enable advanced automation and testing workflows:

Pre-request scripts: Run before a request is sent (set dynamic headers, compute signatures, etc.)
Post-response scripts: Run after receiving a response (validate data, extract values, run tests)

Scripts run in a sandboxed Node.js vm environment with a 2-second timeout and 100KB size limit.

The pm Object

The pm object provides the scripting API. It’s available globally in all scripts.

pm.environment

Access and modify environment variables.

pm.environment.get

function

Get the value of an environment variable.Signature: pm.environment.get(name: string): string | undefined

const apiKey = pm.environment.get('API_KEY');
console.log('Using API key:', apiKey);

pm.environment.set

function

Set or create an environment variable. Changes are persisted to storage.Signature: pm.environment.set(name: string, value: string): void

// Extract token from response and save to environment
const token = pm.response.json().access_token;
pm.environment.set('AUTH_TOKEN', token);

If the variable doesn’t exist, it will be created automatically in the current environment.

pm.environment.unset

function

Remove an environment variable.Signature: pm.environment.unset(name: string): void

pm.environment.unset('TEMP_TOKEN');

pm.globals

Access and modify global variables (shared across all environments).

pm.globals.get

function

Get the value of a global variable.Signature: pm.globals.get(name: string): string | undefined

const baseUrl = pm.globals.get('BASE_URL');

pm.globals.set

function

Set or create a global variable. Changes are persisted to storage.Signature: pm.globals.set(name: string, value: string): void

pm.globals.set('REQUEST_COUNT', '42');

pm.globals.unset

function

Remove a global variable.Signature: pm.globals.unset(name: string): void

pm.globals.unset('TEMP_VALUE');

pm.variables

Read-only access to resolved variables (combines globals, collection, and environment).

pm.variables.get

function

Get the resolved value of a variable following precedence order.Signature: pm.variables.get(name: string): string | undefinedResolution order: Globals → Collection → Environment (narrowest wins)

// Gets the most specific value
const apiUrl = pm.variables.get('API_URL');

Use pm.variables.get() when you don’t care which scope the variable comes from. Use pm.environment.get() or pm.globals.get() when you need a specific scope.

pm.request

Access request data (available in both pre-request and post-response scripts).

pm.request.url

string

The request URL (after variable substitution).

console.log('Sending request to:', pm.request.url);

pm.request.method

string

The HTTP method (GET, POST, PUT, DELETE, etc.).

if (pm.request.method === 'POST') {
  // Add special header for POST requests
  pm.request.headers.add('X-Request-Type', 'mutation');
}

pm.request.headers

object

Request headers collection.Methods:

get(name: string): string | undefined - Get header value
add(name: string, value: string): void - Add header
remove(name: string): void - Remove header

// Add authentication header
const token = pm.environment.get('TOKEN');
pm.request.headers.add('Authorization', `Bearer ${token}`);

// Check existing header
const contentType = pm.request.headers.get('Content-Type');

pm.request.body

object

Request body content.Methods:

raw() - Get body as string
json() - Parse body as JSON (throws if invalid)

// Modify request body
const body = pm.request.body.json();
body.timestamp = new Date().toISOString();
pm.request.body = JSON.stringify(body);

pm.response

Access response data (only available in post-response scripts).

pm.response.code

number

HTTP status code.

pm.test('Status is 200', () => {
  pm.expect(pm.response.code).to.equal(200);
});

pm.response.status

string

HTTP status text (e.g., “OK”, “Not Found”).

console.log('Response status:', pm.response.status);

pm.response.headers

object

Response headers collection.Methods:

get(name: string): string | undefined - Get header value
has(name: string): boolean - Check if header exists

const contentType = pm.response.headers.get('Content-Type');
pm.test('Response is JSON', () => {
  pm.expect(contentType).to.include('application/json');
});

pm.response.body

string

Raw response body as string.

console.log('Response length:', pm.response.body.length);

pm.response.json

function

Parse response body as JSON.Signature: pm.response.json(): any

const data = pm.response.json();
pm.test('Has user ID', () => {
  pm.expect(data.user.id).to.be.a('number');
});

Throws an error if the response body is not valid JSON.

pm.response.time

number

Response time in milliseconds.

pm.test('Response time is acceptable', () => {
  pm.expect(pm.response.time).to.be.below(500);
});

pm.test()

Define a test assertion (post-response scripts only).

pm.test

function

Create a named test with an assertion function.Signature: pm.test(name: string, fn: () => void): void

pm.test('User has valid email', () => {
  const user = pm.response.json();
  pm.expect(user.email).to.match(/@/);
});

Test results are displayed in the “Tests” tab of the response panel.

pm.expect()

ChaiJS-style assertions for testing.

pm.expect

function

Create an assertion using Chai’s expect syntax.Signature: pm.expect(actual): AssertionCommon assertions:

Equality
Type Checking
Comparison
String Matching
Array/Object

pm.expect(actual).to.equal(expected);
pm.expect(actual).to.eql(expected); // deep equality
pm.expect(actual).to.not.equal(value);

pm.expect(value).to.be.a('string');
pm.expect(value).to.be.an('array');
pm.expect(value).to.be.a('number');
pm.expect(value).to.be.true;
pm.expect(value).to.be.null;
pm.expect(value).to.be.undefined;

pm.expect(value).to.be.above(10);
pm.expect(value).to.be.below(100);
pm.expect(value).to.be.at.least(5);
pm.expect(value).to.be.at.most(50);

pm.expect(str).to.include('substring');
pm.expect(str).to.match(/regex/);
pm.expect(str).to.have.lengthOf(10);

pm.expect(array).to.be.an('array').that.is.not.empty;
pm.expect(array).to.have.lengthOf(3);
pm.expect(array).to.include('item');
pm.expect(obj).to.have.property('key');
pm.expect(obj).to.have.all.keys('a', 'b', 'c');

console

Log messages and debugging output.

console.log

function

Log informational messages.Signature: console.log(...args: any[]): void

console.log('Token extracted:', token);
console.log('User data:', user.name, user.email);

console.error

function

Log error messages.Signature: console.error(...args: any[]): void

console.error('Failed to parse response:', error.message);

console.warn

function

Log warning messages.Signature: console.warn(...args: any[]): void

console.warn('Deprecated API endpoint used');

Console output is displayed in the “Tests” tab with a 200-entry limit. Logs are cleared between requests.

Script Examples

Pre-Request Script Examples

Dynamic Headers
Token Refresh
Request Counter

Add computed headers before sending the request:

// Add timestamp header
pm.request.headers.add('X-Request-Time', new Date().toISOString());

// Add HMAC signature
const secret = pm.environment.get('API_SECRET');
const payload = pm.request.body.raw();
const signature = computeHMAC(secret, payload);
pm.request.headers.add('X-Signature', signature);

Check token expiration and refresh if needed:

const expiresAt = pm.globals.get('TOKEN_EXPIRES_AT');
const now = Date.now();

if (!expiresAt || now >= parseInt(expiresAt)) {
  console.log('Token expired, refreshing...');
  // Set flag to trigger token refresh flow
  pm.globals.set('NEEDS_REFRESH', 'true');
}

Track request count:

const count = parseInt(pm.globals.get('REQUEST_COUNT') || '0');
pm.globals.set('REQUEST_COUNT', (count + 1).toString());
console.log('Request number:', count + 1);

Post-Response Script Examples

Extract Token
Response Validation
Extract & Chain
Error Handling

Extract authentication token from response:

const response = pm.response.json();

if (response.access_token) {
  pm.environment.set('AUTH_TOKEN', response.access_token);
  console.log('Token saved to environment');
  
  // Calculate expiration time
  const expiresIn = response.expires_in || 3600;
  const expiresAt = Date.now() + (expiresIn * 1000);
  pm.globals.set('TOKEN_EXPIRES_AT', expiresAt.toString());
}

Validate response structure and data:

pm.test('Status is 200 OK', () => {
  pm.expect(pm.response.code).to.equal(200);
});

pm.test('Response is JSON', () => {
  const contentType = pm.response.headers.get('Content-Type');
  pm.expect(contentType).to.include('application/json');
});

pm.test('Response has required fields', () => {
  const data = pm.response.json();
  pm.expect(data).to.have.property('id');
  pm.expect(data).to.have.property('email');
  pm.expect(data.email).to.be.a('string');
});

pm.test('Response time is acceptable', () => {
  pm.expect(pm.response.time).to.be.below(1000);
});

Extract data for use in subsequent requests:

const user = pm.response.json();

// Save user ID for next request
pm.environment.set('USER_ID', user.id.toString());
pm.environment.set('USER_EMAIL', user.email);

console.log('User created:', user.id, user.email);

pm.test('User ID is valid', () => {
  pm.expect(user.id).to.be.a('number');
  pm.expect(user.id).to.be.above(0);
});

Handle errors gracefully:

if (pm.response.code >= 400) {
  console.error('Request failed:', pm.response.status);
  
  try {
    const error = pm.response.json();
    console.error('Error details:', error.message);
  } catch (e) {
    console.error('Non-JSON error response');
  }
} else {
  pm.test('Request successful', () => {
    pm.expect(pm.response.code).to.be.below(400);
  });
}

Script Limits

Scripts run in a sandboxed environment with the following limits:

Timeout: 2 seconds maximum execution time
Size: 100KB maximum script size
Console output: 200 entries maximum
Test results: 200 tests maximum
No external modules: Cannot use require() or import
No file system access: Cannot read/write files
No network access: Cannot make HTTP requests (except via pm.sendRequest() - coming soon)

Scripts that exceed the timeout or size limit will be terminated and an error will be displayed in the Tests tab.

Postman Compatibility

LiteClient’s scripting API is compatible with Postman Collection v2.1:

Import: Pre-request and test scripts are preserved when importing Postman collections
Export: Scripts are included when exporting to Postman format
Limitations: Collection-level and folder-level scripts are not supported (request-level only)

When importing a collection with collection-level or folder-level scripts, a warning will be displayed. You’ll need to manually copy those scripts to individual requests.

Best Practices

Script Organization

Keep scripts focused on a single responsibility
Use comments to explain complex logic
Extract common logic to environment variables (as JSON strings)
Use meaningful test names that describe what’s being validated

Performance

Avoid expensive operations in pre-request scripts (they delay request sending)
Cache computed values in variables instead of recalculating
Use console.log() sparingly in production scripts

Error Handling

Always wrap JSON parsing in try-catch blocks
Check for variable existence before using them
Provide descriptive error messages in console output
Use tests to validate assumptions about response structure

Variable Management

Use globals for values shared across all requests (base URLs, API keys)
Use environment variables for values specific to an environment (dev/prod tokens)
Use descriptive variable names (avoid single letters)
Clean up temporary variables with unset() when done

Reference

Community

Overview

The pm Object

pm.environment

pm.globals

pm.variables

pm.request

pm.response

pm.test()

pm.expect()

console

Script Examples

Pre-Request Script Examples

Post-Response Script Examples

Script Limits

Postman Compatibility

Best Practices

Script Organization

Performance

Error Handling

Variable Management

Reference

Community

​Overview

​The pm Object

​pm.environment

​pm.globals

​pm.variables

​pm.request

​pm.response

​pm.test()

​pm.expect()

​console

​Script Examples

​Pre-Request Script Examples

​Post-Response Script Examples

​Script Limits

​Postman Compatibility

​Best Practices

​Script Organization

​Performance

​Error Handling

​Variable Management

Overview

The pm Object

pm.environment

pm.globals

pm.variables

pm.request

pm.response

pm.test()

pm.expect()

console

Script Examples

Pre-Request Script Examples

Post-Response Script Examples

Script Limits

Postman Compatibility

Best Practices

Script Organization

Performance

Error Handling

Variable Management