The DefaultValue Post-processing function explains itself by the name (default value). This function can be used in the agents to fill any value, where any cell is by default blank or empty. For example, I have this scraping agent "DefaultValue Function Example (Post-Processing)" in my account which helps to understand the working of DefaultValue Post-processing function. This agent uses the Category field for implementing the default value in each row. If you notice the screenshot below, it clarifies very well.
Edit the scraping agent by clicking on the Edit tab
Go to the field Category and click on the Edit field button
Now click on the Add Post-processing button to add the
DefaultValuefunction, the below dialog box will appear
Now, enter the input text as Mobile, this entered value will be used as default value to fill blank cell
Then Save the function and the scraping agent configuration
And finally, re-run your agent to apply the changes.
After Default Value Function
If you notice the screenshot below, the Category field is updated by
Default Value Post-processing function.