How to check for empty string in Flow studio

This document explains how to check for an Empty string in the Flow studio using Evaluate Control.

In the below example, we will pass an empty string to the Evaluate control using Custom control. Then we will use the Regex code in the Evaluate control to verify the empty string.

Custom control

Use a Custom control in the Flow studio flow to build your custom logic.
In the Experience Designer, place the below code in the Function node to set an empty string.
```
msg.orbita.session.emptyString = "";
return msg;
```

Evaluate control

You have to use the Evaluate control to check for an empty string in flow studio.

Drop the Evaluate control onto the canvas.
Select Custom from the Input node list. (You will have access to the entire msg object when you use Custom from the list.)
In the input field, add the empty string property path (as a mustache tag).
In this example, it is at msg.orbita.session.emptyString
In the pin options, select “matches regex“ from the list and add the below Regex to evaluate.
```
^\s$
```

The regex ^\s$ will match empty string or single space.
If you want to match empty string or multiple spaces, use ^\s*$

How to check for empty string in Flow studio

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