Magento – Magento2: How to change the Shipping Address Form validation message

Create Module and Make Ajax Request as from your Module and Validate in Theme through JS. I will share you some piece of my code. This Code have validate only Postcode(Pincode), you can manipulate it.

Path: OSCP/ModuleName/Controller/Ajax/CheckPincode.php

<?php
namespace OSCP/ModuleName\Controller\Ajax;

use Magento\Framework\App\Action\Action;
use Magento\Framework\App\Action\Context;
use Magento\Framework\View\Result\PageFactory;
use MM\ShippingType\Model\LocalPincode;
use Magento\Checkout\Model\Cart;
use Magento\Catalog\Model\ResourceModel\Product\CollectionFactory as ProductCollectionFactory;

class CheckPincode extends Action
{
    protected $resultPageFactory;

    protected $_storeManager;

    protected $resultRedirectFactory;

    protected $_localPincode;

    protected $_cart;

    protected $_localPostcode;

    public function __construct(
        Context $context,
        PageFactory $resultPageFactory,
        \Magento\Framework\Controller\Result\RedirectFactory $resultRedirectFactory,
        LocalPincode $localPincode,
        Cart $cart,
        ProductCollectionFactory $productCollectionFactory
    ) {
        parent::__construct($context);
        $this->resultPageFactory = $resultPageFactory;
        $this->resultRedirectFactory = $resultRedirectFactory;
        $this->_localPincode = $localPincode;
        $this->_cart = $cart;
        $this->_productCollectionFactory = $productCollectionFactory;
    }

    public function execute()
    {
        $postcode = $this->getRequest()->getParam('pincode');
        $localPostCode = $this->_localPincode->isLocalPostcode($postcode);
        $response = [];
        if (!$localPostCode) {
            $response = ['error' => true, 'message' => 'Sorry, we don\'t deliver to that postcode - please call us for a quote.'];
        }
        echo json_encode($response);
        exit;
    }
}

Path: app/design/frontend/VendorName/ThemeName/Magento_Checkout/web/js/view/shipping.js

define([
    'jquery',
    'underscore',
    'Magento_Ui/js/form/form',
    'ko',
    'Magento_Customer/js/model/customer',
    'Magento_Customer/js/model/address-list',
    'Magento_Checkout/js/model/address-converter',
    'Magento_Checkout/js/model/quote',
    'Magento_Checkout/js/action/create-shipping-address',
    'Magento_Checkout/js/action/select-shipping-address',
    'Magento_Checkout/js/model/shipping-rates-validator',
    'Magento_Checkout/js/model/shipping-address/form-popup-state',
    'Magento_Checkout/js/model/shipping-service',
    'Magento_Checkout/js/action/select-shipping-method',
    'Magento_Checkout/js/model/shipping-rate-registry',
    'Magento_Checkout/js/action/set-shipping-information',
    'Magento_Checkout/js/model/step-navigator',
    'Magento_Ui/js/modal/modal',
    'Magento_Checkout/js/model/checkout-data-resolver',
    'Magento_Checkout/js/checkout-data',
    'uiRegistry',
    'mage/translate',
    'Magento_Checkout/js/model/shipping-rate-service'
], function (
    $,
    _,
    Component,
    ko,
    customer,
    addressList,
    addressConverter,
    quote,
    createShippingAddress,
    selectShippingAddress,
    shippingRatesValidator,
    formPopUpState,
    shippingService,
    selectShippingMethodAction,
    rateRegistry,
    setShippingInformationAction,
    stepNavigator,
    modal,
    checkoutDataResolver,
    checkoutData,
    registry,
    $t
) {
    'use strict';

    var popUp = null;

    return Component.extend({
        defaults: {
            template: 'Magento_Checkout/shipping',
            shippingFormTemplate: 'Magento_Checkout/shipping-address/form',
            shippingMethodListTemplate: 'Magento_Checkout/shipping-address/shipping-method-list',
            shippingMethodItemTemplate: 'Magento_Checkout/shipping-address/shipping-method-item'
        },
        visible: ko.observable(!quote.isVirtual()),
        errorValidationMessage: ko.observable(false),
        isCustomerLoggedIn: customer.isLoggedIn,
        isFormPopUpVisible: formPopUpState.isVisible,
        isFormInline: addressList().length === 0,
        isNewAddressAdded: ko.observable(false),
        saveInAddressBook: 1,
        quoteIsVirtual: quote.isVirtual(),

        /**
         * @return {exports}
         */
        initialize: function () {
            var self = this,
                hasNewAddress,
                fieldsetName = 'checkout.steps.shipping-step.shippingAddress.shipping-address-fieldset';

            this._super();

            if (!quote.isVirtual()) {
                stepNavigator.registerStep(
                    'shipping',
                    '',
                    $t('Shipping'),
                    this.visible, _.bind(this.navigate, this),
                    10
                );
            }
            checkoutDataResolver.resolveShippingAddress();

            hasNewAddress = addressList.some(function (address) {
                return address.getType() == 'new-customer-address'; //eslint-disable-line eqeqeq
            });

            this.isNewAddressAdded(hasNewAddress);

            this.isFormPopUpVisible.subscribe(function (value) {
                if (value) {
                    self.getPopUp().openModal();
                }
            });

            quote.shippingMethod.subscribe(function () {
                self.errorValidationMessage(false);
            });

            registry.async('checkoutProvider')(function (checkoutProvider) {
                var shippingAddressData = checkoutData.getShippingAddressFromData();

                if (shippingAddressData) {
                    checkoutProvider.set(
                        'shippingAddress',
                        $.extend(true, {}, checkoutProvider.get('shippingAddress'), shippingAddressData)
                    );
                }
                checkoutProvider.on('shippingAddress', function (shippingAddrsData) {
                    checkoutData.setShippingAddressFromData(shippingAddrsData);
                });
                shippingRatesValidator.initFields(fieldsetName);
            });

            return this;
        },

        /**
         * Navigator change hash handler.
         *
         * @param {Object} step - navigation step
         */
        navigate: function (step) {
            step && step.isVisible(true);
        },

        /**
         * @return {*}
         */
        getPopUp: function () {
            var self = this,
                buttons;

            if (!popUp) {
                buttons = this.popUpForm.options.buttons;
                this.popUpForm.options.buttons = [
                    {
                        text: buttons.save.text ? buttons.save.text : $t('Save Address'),
                        class: buttons.save.class ? buttons.save.class : 'action primary action-save-address',
                        click: self.saveNewAddress.bind(self)
                    },
                    {
                        text: buttons.cancel.text ? buttons.cancel.text : $t('Cancel'),
                        class: buttons.cancel.class ? buttons.cancel.class : 'action secondary action-hide-popup',

                        /** @inheritdoc */
                        click: this.onClosePopUp.bind(this)
                    }
                ];

                /** @inheritdoc */
                this.popUpForm.options.closed = function () {
                    self.isFormPopUpVisible(false);
                };

                this.popUpForm.options.modalCloseBtnHandler = this.onClosePopUp.bind(this);
                this.popUpForm.options.keyEventHandlers = {
                    escapeKey: this.onClosePopUp.bind(this)
                };

                /** @inheritdoc */
                this.popUpForm.options.opened = function () {
                    // Store temporary address for revert action in case when user click cancel action
                    self.temporaryAddress = $.extend(true, {}, checkoutData.getShippingAddressFromData());
                };
                popUp = modal(this.popUpForm.options, $(this.popUpForm.element));
            }

            return popUp;
        },

        /**
         * Revert address and close modal.
         */
        onClosePopUp: function () {
            checkoutData.setShippingAddressFromData($.extend(true, {}, this.temporaryAddress));
            this.getPopUp().closeModal();
        },

        /**
         * Show address form popup
         */
        showFormPopUp: function () {
            this.isFormPopUpVisible(true);
        },

        /**
         * Save new shipping address
         */
        saveNewAddress: function () {
            var addressData,
                newShippingAddress;
            var thisvar = this;
            this.source.set('params.invalid', false);
            this.triggerShippingDataValidateEvent();

            if (!this.source.get('params.invalid')) {
                addressData = this.source.get('shippingAddress');
                // if user clicked the checkbox, its value is true or false. Need to convert.
                addressData['save_in_address_book'] = this.saveInAddressBook ? 1 : 0;

                var pincode = addressData.postcode;
                $(".error-txt").remove();
                $.ajax({
                    url: '/shippingtype/ajax/checkpincode',
                    type: 'POST',
                    showLoader: true,
                    data: {pincode:pincode},
                    complete: function(response) {
                        var res = JSON.parse(JSON.stringify(response));
                        var responseText = JSON.parse(res.responseText);
                        if (responseText.error == true) {
                            // Display error message exactly after pincode textbox
                            $('#co-shipping-form input[name=postcode]').after('<span class="error-txt" style="color: red;">'+responseText.message+'</span>');
                            return false;
                        } else {
                            newShippingAddress = createShippingAddress(addressData);
                            selectShippingAddress(newShippingAddress);
                            checkoutData.setSelectedShippingAddress(newShippingAddress.getKey());
                            checkoutData.setNewCustomerShippingAddress($.extend(true, {}, addressData));
                            //this.getPopUp().closeModal();
                            thisvar.getPopUp().closeModal();
                            thisvar.isNewAddressAdded(true);
                            return true;

                        }
                    }
                });
            }
        },

        /**
         * Shipping Method View
         */
        rates: shippingService.getShippingRates(),
        isLoading: shippingService.isLoading,
        isSelected: ko.computed(function () {
            return quote.shippingMethod() ?
                quote.shippingMethod()['carrier_code'] + '_' + quote.shippingMethod()['method_code'] :
                null;
        }),

        /**
         * @param {Object} shippingMethod
         * @return {Boolean}
         */
        selectShippingMethod: function (shippingMethod) {
            selectShippingMethodAction(shippingMethod);
            checkoutData.setSelectedShippingRate(shippingMethod['carrier_code'] + '_' + shippingMethod['method_code']);

            return true;
        },

        /**
         * Set shipping information handler
         */
        setShippingInformation: function () {
            /*if (this.validateShippingInformation()) {
                setShippingInformationAction().done(
                    function () {
                        stepNavigator.next();
                    }
                );
            }*/
            if (!this.source.get('params.invalid')) {
                var shippingAdd = this.source.get('shippingAddress');
                //var shippingAdd = quote.shippingAddress();
                var thisObj = this;
                var pincode = shippingAdd.postcode;
                if ($("#co-shipping-form").length && pincode) {
                    $(".error-txt").remove();
                    $.ajax({
                        url: '/shippingtype/ajax/checkpincode',
                        type: 'POST',
                        data: {pincode: pincode},
                        complete: function (response) {
                            var res = JSON.parse(JSON.stringify(response));
                            var responseText = JSON.parse(res.responseText);
                            $(".error-txt").remove();
                            if (responseText.error == true) {
                                // Display error message exactly after pincode textbox
                                $('#co-shipping-form input[name=postcode]').after('<span class="error-txt" style="color: red;">' + responseText.message + '</span>');
                                return false;
                            }
                        }
                    });
                }

                // Call validate shipping function only when your pincode is valid
                if (thisObj.validateShippingInformation()) {
                    setShippingInformationAction().done(
                        function () {
                            stepNavigator.next();
                        }
                    );
                }
            }
        },

        /**
         * @return {Boolean}
         */
        validateShippingInformation: function () {
            var shippingAddress,
                addressData,
                loginFormSelector = 'form[data-role=email-with-possible-login]',
                emailValidationResult = customer.isLoggedIn(),
                field;

            if (!quote.shippingMethod()) {
                this.errorValidationMessage($t('Please specify a shipping method.'));

                return false;
            }

            if (!customer.isLoggedIn()) {
                $(loginFormSelector).validation();
                emailValidationResult = Boolean($(loginFormSelector + ' input[name=username]').valid());
            }

            if (this.isFormInline) {
                this.source.set('params.invalid', false);
                this.triggerShippingDataValidateEvent();

                if (emailValidationResult &&
                    this.source.get('params.invalid') ||
                    !quote.shippingMethod()['method_code'] ||
                    !quote.shippingMethod()['carrier_code']
                ) {
                    this.focusInvalid();

                    return false;
                }

                shippingAddress = quote.shippingAddress();
                addressData = addressConverter.formAddressDataToQuoteAddress(
                    this.source.get('shippingAddress')
                );

                //Copy form data to quote shipping address object
                for (field in addressData) {
                    if (addressData.hasOwnProperty(field) &&  //eslint-disable-line max-depth
                        shippingAddress.hasOwnProperty(field) &&
                        typeof addressData[field] != 'function' &&
                        _.isEqual(shippingAddress[field], addressData[field])
                    ) {
                        shippingAddress[field] = addressData[field];
                    } else if (typeof addressData[field] != 'function' &&
                        !_.isEqual(shippingAddress[field], addressData[field])) {
                        shippingAddress = addressData;
                        break;
                    }
                }

                if (customer.isLoggedIn()) {
                    shippingAddress['save_in_address_book'] = 1;
                }
                selectShippingAddress(shippingAddress);
            }

            if (!emailValidationResult) {
                $(loginFormSelector + ' input[name=username]').focus();

                return false;
            }

            return true;
        },

        /**
         * Trigger Shipping data Validate Event.
         */
        triggerShippingDataValidateEvent: function () {
            this.source.trigger('shippingAddress.data.validate');

            if (this.source.get('shippingAddress.custom_attributes')) {
                this.source.trigger('shippingAddress.custom_attributes.data.validate');
            }
        }
    });
});