Need to override following file rules.js

Question

magento2.3.3/pub/static/adminhtml/Magento/backend/da_DK/Magento_Ui/js/lib/validation/rules.js

I need to override rules.js for specific Danish locale only for Admin area, how can I achieve that.

In short, if I describe then I need to make a small change in validate-number to support 100.000,00

'validate-number': [
            function (value) {
                return utils.isEmptyNoTrim(value) ||
                    !isNaN(utils.parseNumber(value)) && /^\s*-?\d*(.\d*)*(\,\d*)?\s*$/.test(value);
            },

Answer 1

Create requirejs-config.js in Vendor/Module/view/base/.

var config = {
    config: {
        mixins: {
            'Magento_Ui/js/lib/validation/rules': {
                'Vendor_Module/js/lib/validation/rules': true
            }
        }
    }
};

Create rules.js in Vendor/Module/view/base/web/js/lib/validation.

define([
    'jquery',
    'underscore',
    'moment',
    'mage/translate'
], function ($, _, moment) {
    'use strict';

    return function (validator) {
        var validators = {
            'validate-number-custom': [
                function (value) {
                    return /^[a-zA-Z ]*$/i.test(value);
                },
                $.mage.__('Please enter a valid number in this field.')
            ]
        };

        validators = _.mapObject(validators, function (data) {
            return {
                handler: data[0],
                message: data[1]
            };
        });

        return $.extend(validator, validators);
    };
});

Add your changes in return line. And use validate-number-custom validation for your field.

And execute php bin/magento setup:upgrade and php bin/magento setup:static-content:deploy.