Introduction to variables and scripting

Introduction to Variables and Scripting

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This section expands on using variables in Postman and introduces scripting for dynamic request behavior.

Variables in Postman (Continued)

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Variables store reusable values, promoting DRY (Don’t Repeat Yourself) principles and protecting sensitive data like API keys.

Variable Scopes

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Postman variables have different scopes, affecting their accessibility:

• Global: Accessible in all workspaces.
• Collection: Accessible within a collection.
• Environment: Accessible within an environment.
• Data: Used with data files for running multiple iterations of a request.
• Local: Specific to a single request or script.

Postman resolves variable values based on the narrowest available scope. This section focuses on collection variables.

Scripting in Postman

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Postman scripts add dynamic behavior to collections. Scripts execute during two events:

1. Pre-request Script: Runs before a request is sent.
2. Post-request Script: Runs after a response is received.

This section focuses on post-request scripts.

The pm Object

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The pm object provides access to Postman data, including the response body, variables, and utilities.

• pm.response.json(): Accesses the JSON response body.
• pm.collectionVariables.get("variableName"): Retrieves a collection variable’s value.
• pm.collectionVariables.set("variableName", "variableValue"): Sets a collection variable.

Your First Script

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This task introduces a simple post-request script.

1. In the “add book” request, modify the book data in the “Body” tab.
2. In the “Tests” tab, add the following JavaScript code:

console.log(pm.response.json());

3. Save and send the request.

The response data will be logged to the Postman Console.

Capturing the New Book ID

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This task demonstrates setting a variable using a post-request script.

Setting and Getting Collection Variables

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• pm.collectionVariables.set("variableName", value): Sets a collection variable.
• pm.collectionVariables.get("variableName"): Retrieves a collection variable.

Local Variables

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JavaScript const (for constant values) or let (for variable values) keywords can be used to declare local variables within scripts.

Setting the New Book ID as a Variable

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1. In the “add book” request, modify the book data.
2. In the “Tests” tab, replace the previous script with:

// Save the ID from the response
const id = pm.response.json().id;
// Store the ID as a collection variable
pm.collectionVariables.set("id", id);

3. Save and send the request.

The book’s ID from the response is now stored in the id collection variable. This can be verified in the collection’s “Variables” tab. This {{id}} variable can now be used in other requests within the collection.