> For the complete documentation index, see [llms.txt](https://docs.loadmill.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.loadmill.com/test-editor-reference/postscript/running-postscript.md).

# Running Postscript

Running code from postscript

Postscript lets you write and run javascript code on every API response of your flow, allowing you to extract or assert parts of the response in a considerable way to validate your flow accurately.

**Say you have an API call that returns an array of fruits and their properties and you want to verify that a specific fruit is inside that list.**

{% embed url="<https://files.gitbook.com/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LHDbUNdi3wPd9vSolzU%2Fuploads%2FEKWCbzNpqzNkAB7uaeYF%2Fpostscript_1.mp4?alt=media&token=0e318ae5-770c-4f23-b8c2-9dad349c7875>" %}

To better understand this validation, consider the following javascript variable:

```javascript
const fruits = [
    {
     name:"Banana",
     id: 1
    },{
     name:"Orange",
     id: 2
    },{
     name:"Apple",
     id: 3
    },{
     name:"Mango",
     id: 4
    }
   ]
```

There are many ways to verify if `"Orange"` is part of the list. In this example, we’ll use the `Array.some()` method on the array.

{% code overflow="wrap" %}

```javascript
const orangeOnList = fruits.some((fruit)=>fruit.name == "Orange") // returns true
```

{% endcode %}

Similarly, when an API returns an array of fruits and their properties, you can validate the existence of a specific fruit with the exact same code.

{% hint style="info" %}
**Note: The $ (dollar sign) returns the entire API response in object type.**
{% endhint %}

{% embed url="<https://files.gitbook.com/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LHDbUNdi3wPd9vSolzU%2Fuploads%2FbH4MezCbfGzYBg8rRr9m%2Fpostscript_1.mp4?alt=media&token=ba184084-354e-4555-80a2-c111a230e414>" %}

```javascript
const fruits = $; // returns the entire json response in object type.
const orangeOnList = fruits.some((fruit)=>fruit.name == "Orange") // returns true
```

{% embed url="<https://files.gitbook.com/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LHDbUNdi3wPd9vSolzU%2Fuploads%2FJuyy1pQRtnyJfVVu78w5%2Fpostscript_3.mp4?alt=media&token=fce72b47-6a3f-4c01-98d3-88d17477b3ef>" %}