Postman JavaScript reference

Postman provides JavaScript APIs that you can use in your request scripts. The pm object provides most of the functionality for testing your request and response data, with the postman object providing some additional workflow control.

Contents

The pm object

You will carry out most of the Postman JavaScript API functionality using pm.*, which provides access to request and response data, and variables.

Using variables in scripts

You can access and manipulate variables at each scope in Postman using the pm API.

You can use dynamic variables to generate values when your requests run.

Postman supports a variety of variable scopes. The pm object provides methods for accessing global, collection, and environment variables specifically, and pm.variables methods for accessing variables at different scopes as well as setting local variables.

  • Check if there is a Postman variable in the current scope: 
pm.variables.has(variableName:String):function → Boolean
  • Get the value of the Postman variable with the specified name: 
pm.variables.get(variableName:String):function → *
  • Set a local variable with the specified name and value: 
pm.variables.set(variableName:String, variableValue:*):function
  • Return the resolved value of a dynamic variable inside a script using the syntax {{$variableName}}: 
pm.variables.replaceIn(variableName:String):function: → *

For example:

const stringWithVars = pm.variables.replaceIn("Hi, my name is {{$randomFirstName}}");
console.log(stringWithVars);
  • Return an object containing all variables with their values in the current scope. Based on the order of precedence, this will contain variables from multiple scopes. 
pm.variables.toObject():function → Object

Variable scope determines the precedence Postman gives to variables when you reference them, in order of increasing precedence:

  • Global
  • Collection
  • Environment
  • Data
  • Local

The variable with the closest scope overrides any others. For example, if you have variables named score in both the current collection and the active environment, and you call pm.variables.get('score'), Postman will return the current value of the environment variable. When you set a variable value using pm.variables.set, the value is local and will only persist for the current request or collection run. 

//collection var 'score' = 1
//environment var 'score' = 2

//first request run
console.log(pm.variables.get('score'));//outputs 2
console.log(pm.collectionVariables.get('score'));//outputs 1
console.log(pm.environment.get('score'));//outputs 2

//second request run
pm.variables.set('score', 3);//local var
console.log(pm.variables.get('score'));//outputs 3

//third request run
console.log(pm.variables.get('score'));//outputs 2

See the Postman Collection SDK Variables reference for more detail.

You can also access variables defined in the individual scopes via pm.environment, pm.collectionVariables, and pm.globals.

Using environment variables in scripts

Your scripts can use the pm.environment methods to access and manipulate variables in the active (currently selected) environment.

  • The name of the active environment:
pm.environment.name:String
  • Check whether the environment has a variable with the specified name: 
pm.environment.has(variableName:String):function → Boolean
  • Get the variable with the specified name in the active environment: 
pm.environment.get(variableName:String):function → *
  • Set the variable with the specified name and value in the active environment: 
pm.environment.set(variableName:String, variableValue:*):function
  • Return the resolved value of a dynamic variable inside a script using the syntax {{$variableName}}: 
pm.environment.replaceIn(variableName:String):function → *

For example:

//environment has vars firstName and age
const stringWithVars = pm.environment.replaceIn("Hi, my name is {{firstName}} and I am {{age}}.");
console.log(stringWithVars);
  • Return all variables with their values in the active environment in a single object: 
pm.environment.toObject():function → Object
  • Remove a variable from the active environment, specifying the variable by name: 
pm.environment.unset(variableName:String):function
  • Clear all variables in the active environment:
pm.environment.clear():function

Note that your ability to edit variables depends on your access level in the workspace.

Using collection variables in scripts

Your scripts can use the pm.collectionVariables methods to access and manipulate variables in the collection.

  • Check whether there is a variable in the collection with the specified name: 
pm.collectionVariables.has(variableName:String):function → Boolean
  • Return the value of the collection variable with the specified name: 
pm.collectionVariables.get(variableName:String):function → *
  • Set a collection variable with the specified name and value: 
pm.collectionVariables.set(variableName:String, variableValue:*):function
  • Return the resolved value of a dynamic variable inside a script using the syntax {{$variableName}}: 
pm.collectionVariables.replaceIn(variableName:String):function → *

For example:

//collection has vars firstName and age
const stringWithVars = pm.collectionVariables.replaceIn("Hi, my name is {{firstName}} and I am {{age}}.");
console.log(stringWithVars);
  • Return all variables with their values in the collection in an object: 
pm.collectionVariables.toObject():function → Object
  • Remove the specified variable from the collection:
pm.collectionVariables.unset(variableName:String):function
  • Clear all variables from the collection:
pm.collectionVariables.clear():function

Using global variables in scripts

Your scripts can use the pm.globals methods to access and manipulate variables at global scope within the workspace.

  • Check where there is a global variable with the specified name: 
pm.globals.has(variableName:String):function → Boolean
  • Return the value of the global variable with the specified name: 
pm.globals.get(variableName:String):function → *
  • Set a global variable with specified name and value:
pm.globals.set(variableName:String, variableValue:*):function
  • Return the resolved value of a dynamic variable inside a script using the syntax {{$variableName}}: 
pm.globals.replaceIn(variableName:String):function → String

For example:

//globals include vars firstName and age
const stringWithVars = pm.globals.replaceIn("Hi, my name is {{firstName}} and I am {{age}}.");
console.log(stringWithVars);
  • Return all global variables and their values in an object: 
pm.globals.toObject():function → Object
  • Remove the specified global variable:
pm.globals.unset(variableName:String):function
  • Clear all global variables in the workspace:
pm.globals.clear():function

Note that your ability to edit variables depends on your access level in the workspace.

Using data variables in scripts

Your scripts can use the pm.iterationData methods to access and manipulate variables from data files during a collection run.

  • Check whether a variable with the specified name exists in the current iteration data: 
pm.iterationData.has(variableName:String):function → boolean
  • Return a variable from the iteration data with the specified name: 
pm.iterationData.get(variableName:String):function → *
  • Return the iteration data variables in an object:
pm.iterationData.toObject():function → Object
  • Convert the iterationData object to JSON format:
pm.iterationData.toJSON():function → *
  • Remove the specified variable:
pm.iterationData.unset(key:String):function

Scripting with request and response data

A variety of methods provide access to request and response data in Postman scripts, including pm.request, pm.response, pm.info, and pm.cookies. Additionally you can send requests using pm.sendRequest.

Scripting with request data

The pm.request object provides access to the data for the request the script is running within. For a Pre-request Script this is the request that is about to run, and for a Test script this is the request that has already run.

You can use the pm.request object pre-request scripts to alter various parts of the request configuration before it runs.

The pm.request object provides the following properties and methods:

  • The request URL:
pm.request.url:Url
pm.request.headers:HeaderList
  • The HTTP request method:
pm.request.method:String
  • The data in the request body. This object is immutable and cannot be modified from scripts: 
pm.request.body:RequestBody
  • Add a header with the specified name and value for the current request: 
pm.request.headers.add(header:Header):function

For example:

pm.request.headers.add({
  key: "client-id",
  value: "abcdef"
});
  • Delete the request header with the specified name:
pm.request.headers.remove(headerName:String):function
  • Insert the specified header name and value (if the header does not exist, otherwise the already existing header will update to the new value): 
pm.request.headers.upsert({key: headerName:String, value: headerValue:String}):function)

See the Postman Collection SDK Request reference for more detail.

Scripting with response data

The pm.response object provides access to the data returned in the response for the current request in scripts added to the Tests.

The pm.response object provides the following properties and methods:

  • The response status code:
pm.response.code:Number
  • The status text string:
pm.response.status:String
pm.response.headers:HeaderList
  • The time the response took to receive in milliseconds: 
pm.response.responseTime:Number
  • The size of the response received:
pm.response.responseSize:Number
  • The response text:
pm.response.text():Function → String
  • The response JSON, which you can use to drill down into the properties received: 
pm.response.json():Function → Object

See the Postman Collection SDK Response reference for more detail.

Scripting with request info

The pm.info object provides data related to the request and the script itself, including name, ID, and iteration count.

The pm.info object provides the following properties and methods:

  • The event, which will be either "prerequest" or "test" depending on where the script is executing within the request: 
pm.info.eventName:String
pm.info.iteration:Number
  • The total number of iterations that are scheduled to run: 
pm.info.iterationCount:Number
  • The saved name of the request running:
pm.info.requestName:String
  • A unique GUID that identifies the running request:
pm.info.requestId:String

Scripting with request cookies

The pm.cookies object provides access to the list of cookies associated with the request.

The pm.cookies object provides the following properties and methods:

  • Check whether a particular cookie (specified by name) exists for the requested domain: 
pm.cookies.has(cookieName:String):Function → Boolean
  • Get the value of the specified cookie:
pm.cookies.get(cookieName:String):Function → String
  • Get a copy of all cookies and their values in an object. Returns any cookies that are defined for the request domain and path: 
pm.cookies.toObject():Function → Object

See the Postman Collection SDK Cookie List reference for more detail.

You can also use pm.cookies.jar to specify a domain for access to request cookies.

To enable programmatic access via the pm.cookies.jar methods, first whitelist the cookie URL.

  • Access the cookie jar object:
pm.cookies.jar():Function → Object

For example:

const jar = pm.cookies.jar();
//cookie methods...
  • Set a cookie using name and value:
jar.set(URL:String, cookie name:String, cookie value:String, callback(error, cookie)):Function → Object
jar.set(URL:String, { name:String, value:String, httpOnly:Bool }, callback(error, cookie)):Function → Object

For example:

const jar = pm.cookies.jar();
jar.set("httpbin.org", "session-id", "abc123", (error, cookie) => {
  if (error) {
    console.error(`An error occurred: ${error}`);
  } else {
    console.log(`Cookie saved: ${cookie}`);
  }
});
  • Get a cookie from the cookie jar:
jar.get(URL:String, cookieName:String, callback (error, value)):Function → Object
  • Get all the cookies from the cookie jar. The cookies are available in the callback function: 
jar.getAll(URL:String, callback (error, cookies)):Function
  • Remove a cookie:
jar.unset(URL:String, token:String, callback(error)):Function → Object
  • Clear all cookies from the cookie jar:
jar.clear(URL:String, callback (error)):Function → Object

See the Postman Collection SDK Cookie reference for more detail.

Sending requests from scripts

You can use the pm.sendRequest method to send a request asynchronously from a Pre-request or Test script. This allows you to execute logic in the background if you are carrying out computation or sending multiple requests at the same time without waiting for each to complete. You can avoid blocking issues by adding a callback function so that your code can respond when Postman receives a response. You can then carry out any additional processing you need on the response data.

You can pass the pm.sendRequest method a URL string, or can provide a complete request configuration in JSON including headers, method, body, and more. 

// Example with a plain string URL
pm.sendRequest('https://postman-echo.com/get', (error, response) => {
  if (error) {
    console.log(error);
  } else {
  console.log(response);
  }
});

// Example with a full-fledged request
const postRequest = {
  url: 'https://postman-echo.com/post',
  method: 'POST',
  header: {
    'Content-Type': 'application/json',
    'X-Foo': 'bar'
  },
  body: {
    mode: 'raw',
    raw: JSON.stringify({ key: 'this is json' })
  }
};
pm.sendRequest(postRequest, (error, response) => {
  console.log(error ? error : response.json());
});

// Example containing a test
pm.sendRequest('https://postman-echo.com/get', (error, response) => {
  if (error) {
    console.log(error);
  }

  pm.test('response should be okay to process', () => {
    pm.expect(error).to.equal(null);
    pm.expect(response).to.have.property('code', 200);
    pm.expect(response).to.have.property('status', 'OK');
  });
});

See the Request definition and Response structure reference docs for more detail.

Scripting workflows

The postman object provides the setNextRequest method for building request workflows when you use the collection runner or Newman.

Note that setNextRequest has no effect when you run requests using the Send button, it only comes into effect when you run a collection.

When you run a collection (using the collection runner or Newman), Postman will run your requests in a default order or an order you specify when you set up the run. However, you can override this execution order using postman.setNextRequest to specify which request should run next.

  • Run the specified request after this one (the request name as defined in the collection e.g. "Get customers"): 
postman.setNextRequest(requestName:String):Function
  • Run the specified request after this one (the request ID returned by pm.info.requestId): 
postman.setNextRequest(requestId:String):Function

For example:

//script in another request calls:
//pm.environment.set('next', pm.info.requestId)
postman.setNextRequest(pm.environment.get('next'));

Scripting visualizations

Use pm.visualizer.set to specify a template to display response data in the visualizer. 

pm.visualizer.set(layout:String, data:Object, options:Object):Function
  • layout required
  • data optional
    • JSON object that binds to the template and you can access it inside the template string
  • options optional

Example usage:

var template = `<p>{{res.info}}</p>`;
pm.visualizer.set(template, {
    res: pm.response.json()
});

Building response data into visualizations

Use pm.getData to retrieve response data inside a visualization template string. 

pm.getData(callback):Function

The callback function accepts two parameters:

Example usage:

pm.getData(function (error, data) {
  var value = data.res.info;
});

Writing test assertions

  • pm.test(testName:String, specFunction:Function):Function

You can use pm.test to write test specifications inside either the Pre-request or Tests scripts. Tests include a name and assertion—Postman will output test results as part of the response.

The pm.test method returns the pm object, making the call chainable. The following sample test checks that a response is valid to proceed. 

pm.test("response should be okay to process", function () {
  pm.response.to.not.be.error;
  pm.response.to.have.jsonBody('');
  pm.response.to.not.have.jsonBody('error');
});

An optional done callback can be passed to pm.test, to test asynchronous functions. 

pm.test('async test', function (done) {
  setTimeout(() => {
    pm.expect(pm.response.code).to.equal(200);
    done();
  }, 1500);
});
  • Get the total number of tests executed from a specific location in code: 
pm.test.index():Function → Number

The pm.expect method allows you to write assertions on your response data, using ChaiJS expect BDD syntax. 

pm.expect(assertion:*):Function → Assertion

You can also use pm.response.to.have.* and pm.response.to.be.* to build your assertions.

See Test examples for more assertions.

Using external libraries 

require(moduleName:String):function → *

The require method allows you to use the sandbox built-in library modules. The list of available libraries is listed below with links to the corresponding documentation.

A number of NodeJS modules are also available to use in the sandbox:

In order to use a library, call the require method, pass the module name as a parameter, and assign the return object from the method to a variable.

Next steps

You can use tests to build Postman into your development projects in a variety of ways using Postman utilities.

Last modified: 2022/02/08