Include jquery, owl carousel, bootstrapjs in magento 2

 app/design/frontend/Vendor/Theme/Magento_Theme/layout/default.xml

 

 <referenceContainer name="after.body.start">
        <block class="Magento\Framework\View\Element\Template" name="custom.js" template="Magento_Theme::custom_js.phtml"/>
  </referenceContainer>

app/design/frontend/Vendor/Theme/requirejs-config.js

/**
 * Copyright © 2015 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */

var config = {
    map: {
        '*': {
            'respond': 'js/respond.min',
            'customScript':'js/customscript'
        }
    },
    paths: {
            'bootstrap': 'js/bootstrap.min',
            'owl_carousel': 'js/owl.carousel',
            'custom':'js/custom',
    },
    shim: {
        'bootstrap': {
            'deps': ['jquery']
        },
        'owl_carousel': {
            'deps': ['jquery']
        },
         'custom': {
            'deps': ['jquery']
        },
    }
};


 

 

app/design/frontend/Vendor/Theme/Magento_Theme/web/js/customscript.js

define('jquery', function($) { //Your code here //alert('Here'); }(jQuery) ); 

 

 

Our template will call our script: app/design/frontend/Vendor/Theme/Magento_Theme/templates/custom_js.phtml

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

 

 

Clear Magento Cache and run static content deploy: php bin/magento setup:static-content:deploy