Base question about flow designer

[heeeding]

I started to learn flow designer, and can't get this part.

First, my trigger is scheduled to run once on the 1st of every month.
Actions are set up as you can see in my picture I included.
I don't know because the field(stock) has been set up to integer,

when I try to choose the field name, it gets updated with only numbers it allows me to write.

so I think I tried every possibe ways to write my script,
to +(plus)10 ((for example)) to current stock value
after i run a test, i get three result.
1. I only get 'u_stock=' on the feild that appears with runtime value
2. error comes up with the words 'u_stock(field name)=fd-scripted'
3. or it says test error when I try to do as I posted.

Did I do something wrong?
What is the problem?
How can I sove this?
Is something wrong with my script? (could you correct it if it is)
Any ways to write the propper script?
Any examples I can get to fix my script?

var currentStock = parseInt(fd_data.action_inputs.u_stock);
var updatedStock = currentStock + 10;
return updateStock;

[Ramesh_Naidu]

Hi @heeeding ,

In the Actions the 1st step can be to use lookup record and later to update the record. Have attached a sample flow below to reference.

Thankyou.

[Sandeep Rajput · Accepted solution]

@heeeding In your flow, the flow script is crashing as it can't access u_stock property on fd_data.action_input. it seems that the action_input object is null hence the property u_stock can't be found on it.

Either use a look up record step to get the value of stock or set a local variable in the flow from where you can derive the value of u_stock.

Hope this helps.