Ttdfjt

In core using KO address is get like this in details.html file

 <!-- ko text: currentBillingAddress().prefix --><!-- /ko --> <!-- ko text: currentBillingAddress().firstname --><!-- /ko --> <!-- ko text: currentBillingAddress().middlename --><!-- /ko -->
<!-- ko text: currentBillingAddress().lastname --><!-- /ko --> <!-- ko text: currentBillingAddress().suffix --><!-- /ko --><br/>
<!-- ko text: _.values(currentBillingAddress().street).join(", ") --><!-- /ko --><br/>
<!-- ko text: currentBillingAddress().city --><!-- /ko -->, <span data-bind="html: currentBillingAddress().region"></span> <!-- ko text: currentBillingAddress().postcode --><!-- /ko --><br/>
<!-- ko text: getCountryName(currentBillingAddress().countryId) --><!-- /ko --><br/>
<!-- ko if: (currentBillingAddress().telephone) -->

This is currentbillingaddress but i want to get defaultbillingaddress in the same way this is, someone any idea

UI component Magento_Checkout/js/view/billing-address doesn't expose the defaultBillingAddress property to the html template, we need to create a new one for that.

Please see the screenshot and try the full code of the billing-address.js below:

/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

define([
 'ko',
 'underscore',
 'Magento_Ui/js/form/form',
 'Magento_Customer/js/model/customer',
 'Magento_Customer/js/model/address-list',
 'Magento_Checkout/js/model/quote',
 'Magento_Checkout/js/action/create-billing-address',
 'Magento_Checkout/js/action/select-billing-address',
 'Magento_Checkout/js/checkout-data',
 'Magento_Checkout/js/model/checkout-data-resolver',
 'Magento_Customer/js/customer-data',
 'Magento_Checkout/js/action/set-billing-address',
 'Magento_Ui/js/model/messageList',
 'mage/translate',
 'Magento_Checkout/js/model/shipping-rates-validator'
],
function (
 ko,
 _,
 Component,
 customer,
 addressList,
 quote,
 createBillingAddress,
 selectBillingAddress,
 checkoutData,
 checkoutDataResolver,
 customerData,
 setBillingAddressAction,
 globalMessageList,
 $t,
 shippingRatesValidator
) 
 'use strict';

 var lastSelectedBillingAddress = null,
 newAddressOption = 
 /**
 * Get new address label
 * @returns String
 */
 getAddressInline: function () 
 return $t('New Address');
 ,
 customerAddressId: null
 ,
 countryData = customerData.get('directory-data'),
 addressOptions = addressList().filter(function (address) 
 return address.getType() == 'customer-address'; //eslint-disable-line eqeqeq
 );

 var defaultBillingAddresses = addressList().filter(function (address) 
 return address.getType() == 'customer-address' && address.isDefaultBilling();
 );

 addressOptions.push(newAddressOption);

 return Component.extend(
 defaults: 
 template: 'Magento_Checkout/billing-address'
 ,
 currentBillingAddress: quote.billingAddress,
 addressOptions: addressOptions,
 customerHasAddresses: addressOptions.length > 1,
 defaultBillingAddress: ko.observable(defaultBillingAddresses[0]),

 /**
 * Init component
 */
 initialize: function () 
 this._super();
 quote.paymentMethod.subscribe(function () 
 checkoutDataResolver.resolveBillingAddress();
 , this);
 shippingRatesValidator.initFields(this.get('name') + '.form-fields');
 ,

 /**
 * @return exports.initObservable
 */
 initObservable: function () 
 this._super()
 .observe( addressOptions.length === 1,
 isAddressSameAsShipping: false,
 saveInAddressBook: 1
 );

 quote.billingAddress.subscribe(function (newAddress) 
 if (quote.isVirtual()) 
 this.isAddressSameAsShipping(false);
 else 
 this.isAddressSameAsShipping(
 newAddress != null &&
 newAddress.getCacheKey() == quote.shippingAddress().getCacheKey() //eslint-disable-line eqeqeq
 );
 

 if (newAddress != null && newAddress.saveInAddressBook !== undefined) 
 this.saveInAddressBook(newAddress.saveInAddressBook);
 else 
 this.saveInAddressBook(1);
 
 this.isAddressDetailsVisible(true);
 , this);

 return this;
 ,

 canUseShippingAddress: ko.computed(function () 
 return !quote.isVirtual() && quote.shippingAddress() && quote.shippingAddress().canUseForBilling();
 ),

 /**
 * @param Object address
 * @return *
 */
 addressOptionsText: function (address) 
 return address.getAddressInline();
 ,

 /**
 * @return Boolean
 */
 useShippingAddress: function () 
 if (this.isAddressSameAsShipping()) 
 selectBillingAddress(quote.shippingAddress());

 this.updateAddresses();
 this.isAddressDetailsVisible(true);
 else 
 lastSelectedBillingAddress = quote.billingAddress();
 quote.billingAddress(null);
 this.isAddressDetailsVisible(false);
 
 checkoutData.setSelectedBillingAddress(null);

 return true;
 ,

 /**
 * Update address action
 */
 updateAddress: function () 
 var addressData, newBillingAddress;

 if (this.selectedAddress() && this.selectedAddress() != newAddressOption) //eslint-disable-line eqeqeq
 selectBillingAddress(this.selectedAddress());
 checkoutData.setSelectedBillingAddress(this.selectedAddress().getKey());
 else 
 this.source.set('params.invalid', false);
 this.source.trigger(this.dataScopePrefix + '.data.validate');

 if (this.source.get(this.dataScopePrefix + '.custom_attributes')) 
 this.source.trigger(this.dataScopePrefix + '.custom_attributes.data.validate');
 

 if (!this.source.get('params.invalid')) 
 addressData = this.source.get(this.dataScopePrefix);

 if (customer.isLoggedIn() && !this.customerHasAddresses) //eslint-disable-line max-depth
 this.saveInAddressBook(1);
 
 addressData['save_in_address_book'] = this.saveInAddressBook() ? 1 : 0;
 newBillingAddress = createBillingAddress(addressData);

 // New address must be selected as a billing address
 selectBillingAddress(newBillingAddress);
 checkoutData.setSelectedBillingAddress(newBillingAddress.getKey());
 checkoutData.setNewCustomerBillingAddress(addressData);
 
 
 this.updateAddresses();
 ,

 /**
 * Edit address action
 */
 editAddress: function () 
 lastSelectedBillingAddress = quote.billingAddress();
 quote.billingAddress(null);
 this.isAddressDetailsVisible(false);
 ,

 /**
 * Cancel address edit action
 */
 cancelAddressEdit: function () 
 this.restoreBillingAddress();

 if (quote.billingAddress()) 
 // restore 'Same As Shipping' checkbox state
 this.isAddressSameAsShipping(
 quote.billingAddress() != null &&
 quote.billingAddress().getCacheKey() == quote.shippingAddress().getCacheKey() && //eslint-disable-line
 !quote.isVirtual()
 );
 this.isAddressDetailsVisible(true);
 
 ,

 /**
 * Restore billing address
 */
 restoreBillingAddress: function () 
 if (lastSelectedBillingAddress != null) 
 selectBillingAddress(lastSelectedBillingAddress);
 
 ,

 /**
 * @param Object address
 */
 onAddressChange: function (address) 
 this.isAddressFormVisible(address == newAddressOption); //eslint-disable-line eqeqeq
 ,

 /**
 * @param Number countryId
 * @return *
 */
 getCountryName: function (countryId) 
 return countryData()[countryId] != undefined ? countryData()[countryId].name : ''; //eslint-disable-line
 ,

 /**
 * Trigger action to update shipping and billing addresses
 */
 updateAddresses: function () 
 if (window.checkoutConfig.reloadOnBillingAddress ,

 /**
 * Get code
 * @param Object parent
 * @returns String
 */
 getCode: function (parent) 
 return _.isFunction(parent.getCode) ? parent.getCode() : 'shared';
 
 );
);*

After that, on the billing-address/details.html you can use defaultBillingAddress().firstname, defaultBillingAddress().lastname, etc

I was messing around with plugins to pass additional customer info through to knockout. I think you could do this

Xml

https://github.com/DominicWatts/CustomerLogin/blob/master/etc/di.xml

Plugin

https://github.com/DominicWatts/CustomerLogin/blob/master/Plugin/Magento/Customer/CustomerData/Customer.php

Template phtml

https://github.com/DominicWatts/CustomerLogin/blob/master/view/frontend/templates/index/index.phtml#L19-L24