Two methods of concatenating 3 variables with a space in this post. I'm going to summarize both methods so the solution is clear. For this example feel free to use the layer mentioned below. I have left it editable, so that you can test out the differences of the two methods . Using Arcade is the most straight forward and flexible depending on how you plan to use the created field.
Example Web Map and layer
https://www.arcgis.com/home/webmap/viewer.html?webmap=1267db066ab144e086f84801f5022ef6
Create an Arcade expression for displaying in pop ups (or labels or symbology). Arcade can be used to display formatted data as a new field in pop ups or for symbology. If you are using Arcade, any updates to existing data will be displayed in the expression as the expression is created at the time of the pop up to display up to date values.
Steps:
1. Add layer to Web Map: https://www.arcgis.com/home/item.html?id=7810a6a9ccd0406fb3b7ce7f10aac818
2. Configure Pop Up > Add Attribute Expression
3. Add Expression: Concatenate([$feature.dog1,$feature.dog2,$feature.dog3], ' ')
4. Ensure the created expression is checked to display in pop up (all dogs in this example)
Note: If you want to use this expression as a label or for symbolization, Click New Expression and then select the existing expression to use in web map
Calculate a field value in a table. You can calculate a concatenated field using the calculate field to. This is great for one time changes to data sets. The data will be updated at the time of the calculation and then may need to be updated manually or by calculation if the contributing fields were to change.
Steps:
1. Display data table in Map Viewer or on Data tab of item details page.
2. Add a field to the table (Calculated Field)
3. Ensure the Field is displaying in the table and select calculate
4. Enter the following calculation:
CONCAT(dog1,CONCAT(' ', CONCAT(dog2,CONCAT(' ',dog3 ))))
5. Verify that the calculated field displays correctly.
