Scripting in Bruno

The backstory

During engagements I use code for automation, to manipulate or modify request/payloads, as well as creating dynamic values. This time around I wanted to leverage the scripting capabilities of Bruno, instead of using a stand alone script. I am going to break down how you can use scripts (dynamic code) within your request Lets get to it…

POC or GTFO…

In this exercise I am going to show how to use a script to create a dynamic value for a GUID in a variable used in the body of the request. It sounds a bit more complicated then it actually is, stick with me ;).

Create a variable in the request by going to Vars -> “+ Add” -> Name it “myGUID” and you can leave a blank value.
Add the myGUID variable within the Body of the request by encapsulating the variable name in double curly brackets, like so: ``. Here is an example of the JSON Body of a request using it:
```
 {
     "Random Guid": "{{myGUID}}",
 }
```

In the Script section, in the Pre Request section add the following code:

 function generateGUID() {
     function s4() {
         return Math.floor((1 + Math.random()) * 0x10000)
             .toString(16)
             .substring(1);
     }
     return s4() + s4() + '-' + s4() + '-' + s4() + '-' + s4() + '-' + s4() + s4() + s4();
 }
	
 const newGUID = generateGUID();
 bru.setVar("myGUID",newGUID)

To summarize, when you execute the request:

The Pre Request script executes
It creates a new GUID and sets that new GUID in the myGUID variable using bru.setVar("myGUID",newGUID)
Since the myGUID is used within the Body of the request, it is replaced with the new value of myGUID
The request is sent with that dynamically generated value

[!TIP] You can also use the variables in other places not limited to the Headers and the endpoint URL