priority of client script and ui policy

aditya2byte · a month ago

ui policy setvisible=true

client script setVisible=false

Clien script over rides ui policy

but for setmandatory and set readonly ui policy over rides client script

so why in first case ,client script over rides ui policy

Ajay_Chavan · 4 weeks ago

Why Client Script Overrides UI Policy for setVisible:

Timing: Client scripts run after UI policies
Last Action Wins: Whatever executes last determines final visibility
No Form Validation: Visibility is just DOM manipulation


Why UI Policy Overrides Client Script for setMandatory/setReadonly:

Form Engine Control: UI Policy engine has higher precedence for form validation
Built-in Protection: ServiceNow protects mandatory/readonly settings at form level
Validation Priority: Form validation rules override client-side changes

Execution Order:
1. Form Loads
2. UI Policies Execute  
3. Client Scripts Execute (onLoad)
4. Field Changes → UI Policies → Client Scripts (onChange)

Summary:
setVisible: Pure DOM manipulation → Last script wins (Client Script)
setMandatory/setReadonly: Form validation → UI Policy precedence (System protection)
Key Point: ServiceNow treats visibility as presentation but mandatory/readonly as form validation rules with different priority systems.

Glad I could help! If this solved your issue, please mark it as ✅ Helpful and ✅ Accept as Solution so others can benefit too.*****Chavan A.P. | Technical Architect | Certified Professional*****

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Bhimashankar H · a month ago

Hi @aditya2byte ,

Are you using all three on same field? check script should not run after all loading then it will override.

Starting with the Istanbul release, ServiceNow began intentionally blocking g_form.setVisible() on mandatory fields. This ensures that the user can always see and fill out a required field, regardless of any conflicting client script logic. Before Istanbul, a client script with setVisible=false could successfully hide a field, potentially conflicting with UI policies and causing issues.

As always Client Script first then UI Policy runs.

Refer this article from SN: KB Article on setMandatory, setVisible issue

Thanks,
Bhimashankar H

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aditya2byte · 4 weeks ago

im not implementing all 3 conditions at time,im executing these 3 conditions separately .

For setReadonly and setMandatory ui policy over ride the client script but for setVisible ui policy doesn't

override the client script , so why

?

Bhimashankar H · 3 weeks ago

@aditya2byte Sometimes there be race condition between UI Policy and Client Script and we run into unexpected behaviour.

So follow the best practice on both the thing, do no use both on same variable.

Thanks,
Bhimashankar H

-------------------------------------------------------------------------------------------------
If my response points you in the right directions, please consider marking it as 'Helpful' & 'Correct'. Thanks!

Bhuvan · a month ago

@aditya2byte

Best practice is not to use both client script and UI policy on same field. Where possible, create UI policy as it is the recommended option.

The issue you are facing could be due to race condition between Client Script and UI Policy and sometimes behavior could be unexpected due to exception scenarios. Refer below link for more details,

https://www.servicenow.com/community/developer-forum/client-script-overriding-the-ui-policy-and-maki...

Mitigate this by having only UI policy and removing client script as both achieve same function.

If this helped to answer your query, please mark it as helpful & accept the solution.

Thanks,

Bhuvan