How to add custom validation rule to billing address field Magento 2

Question

I am using magento 2.1.7. I have added vat field to billing address form. I want to add custom field validation. i have added below code.

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Added below validation to phtml file

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But my custom validation not working. Magento required field validation is working fine. Can anyone help me.

• Jaisa: Hi @Prashant , didd you found the solution
• Prashant Valanda: @sri as per given answer i have override rules js file. add your custom validation to override js file

Answer 1

Override rules.js using below code in my custom module

app/code/Test/Custom/view/frontend/requirejs-config.js

var config = {
 "map": {
 "*" : {
 'Magento_Ui/js/lib/validation/rules' : 'Test_Custom/js/validation/rules'
 }
 }
};

created js file at app/code/Test/Custom/view/frontend/web/js/validation/rules.js

Run php bin/magento setup:static-content:deploy command.

• LucScu: great, it works! Haven't you found another way without override rules.js?
• Prashant Valanda: There is mixin concept but that is not working in my case. Please try with mixin
• LucScu: yes, i could try to override rules.js, thx very much