The ajax method not sending the url to server

I am building a ecommerce project

in that , on index page product when i click on add To cart it should start a AJAX Request, it is going to class and fetching product id but i think not working ajax() method i.e sending url

button in index.blade.php

<button class="product_cart_button addcart" 
    data-id="" >Add to Cart</button>

script code for AJAX

<script type="text/javascript">
    $(document).ready(function(){
        $('.addcart').on('click',function(){
            var id = $(this).data('id') ;
            alert(id);

            if(id){
                $.ajax({
                    url: " / "+ id ,
                    type:"GET",
                    dataType : "json" ,
                    success:function(data){
                            alert('in success function');

alert(id) is working , but second alert not working

on server side

//Route::get('add/to/cart/{id}','CartController@AddCart');

Route::get('add/to/cart/{id}',function(){
     return 'for testing url of ajax entering in web.php';
});

what may be problem I have two script for ajax , anathor for add to wishlist that is working fine , and this script is above that, even I tried it pasting below that but ordering not helping.

addToWishlist ajax code also has

$(document).ready(function(){
    $('.addcart').on('click',function(){

these two same method can this be cause but i tried changing first function to functionTwo() even that not helping , Help Please