How to call front controller from javascript?

Can you share your js, if you use an jquery widget you can pass the url as options But if you have a simple js you can define your car in phtml

<script>
     var url = '<?php echo $this->getUrl('test'); ?>'
</script>

You can use the code below your own Action in controller to call url from Ajax. Using phtml file.

In your (Like vendor/module/Block/Example.php) block put below code.

public function getAjaxUrl(){
    return $this->getUrl("module/index/view"); // Controller Url
}

Put below code view/fronted/templates/example.phtml

<script>
    require(
        ['jquery','example'],
        function($,example){

        var ajaxurl = '<?php echo $block->getAjaxUrl() ?>';
        example.exampleData(ajaxurl);

    }); 
</script>

Put below code view/fronted/web/js/example.js

define([
        'jquery',
        ],
    function($,example){

    return {
        exampleData:function(ajaxurl){
        $(document).on('click','.example-list',function (event){
                event.preventDefault();
                var id=$(this).attr('id');
                $.ajax({
                    url:ajaxurl,
                    type:'POST',
                    showLoader: true,
                    dataType:'json',
                    data: {id:id},                                      
                    success:function(response){
                        //put your code
                    }
                });
            });
        }
    }

});

Your own controller like vendor/module/Controller/Index/View.php

namespace Vendor\Module\Controller\Index;

use Magento\Framework\View\Result\PageFactory; use Magento\Framework\App\Action\Context; use Vendor\Module\Model\ResourceModel\Example\CollectionFactory;

class View extends \Magento\Framework\App\Action\Action
{

    protected $resultPageFactory;

    public function __construct(
        Context $context,
        CollectionFactory $exampleFactory,
        PageFactory $resultPageFactory
    ) {
        $this->resultPageFactory = $resultPageFactory;
        $this->exampleFactory = $exampleFactory;
        parent::__construct($context);
    }
    /**
     * Index action
     *
     * @return $this
     */
    public function execute()
    {
        /*Put below your code*/
        $id = $this->getRequest()->getParam('id', false);
        $responseData = $this->exampleFactory->create();

        $resultJson = $this->resultFactory->create(ResultFactory::TYPE_JSON);
        $resultJson->setData($responseData);
        return $resultJson;
    }
}

Hope this will help.