Create **customer_account_create.xml** at

*app/code/MyModulespace/ModuleName/view/frontend/layout/customer_account_create.xml*

    <?xml version="1.0"?>
    <page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
        <head>
            <script src="MyModulespace_ModuleName::js/myjs.js"/>
            <css src="MyModulespace_ModuleName::css/mycss.css" />
        </head>
    </page>

Also, keep **Magento_Customer** in a sequence of your module

*app/code/MyModulespace/ModuleName/etc/module.xml*

    <?xml version="1.0"?>
    <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
        <module name="MyModulespace_ModuleName" setup_version="1.0.0">
            <sequence>
                <module name="Magento_Customer"/>
            </sequence>
        </module>
    </config>

> **Add custom js via `requirejs-config.js`**

*app/code/MyModulespace/ModuleName/view/frontend/requirejs-config.js*

    var config = {
        map: {
            '*': {
                myjs:'MyModulespace_ModuleName/myjs'
            }
        }
    };


*app/code/MyModulespace/ModuleName/web/js/myjs.js*

    define('jquery', function($) {

        //Your custom js code here

        }(jQuery)
    );

Then you can use custom js in registration template

    <script>
    // <![CDATA[
        require(['jquery','myjs'], function ($, myjs) {
            //Your code
        });
    // ]]>
    </script>