How to disable scrolling in the background when the mobile menu is open?

Question

I am building a mobile responsive website that has a nav menu. When I get to the bottom of the menu - If I continue scrolling when I reach the bottom of the menu - it scrolls the page in the background. How can I disable it?

This is my jQuery code so far:

// When the document is loaded...
$(document).ready(function() {

    $('#mob-menu-btn').click(function(){
        $('.sports').slideToggle("slow");
    })

    $('#sub-menu').click(function(){
        $('.sports2').slideToggle("slow");
    })

});

and this is my CSS:

    .list{
        width: 100%;
        overflow: hidden;
        overflow-y: auto;
        top: -10%;
        overflow: hidden;
        overflow-y: auto;
}


    .sports li{
        list-style-image:none;
        list-style-type: none;
        border-bottom: 2px solid #eeeeee;
        margin-bottom: 0px; 
        margin-left: 0px; 
        padding-top: 15px;
        padding-bottom: 15px;
        padding-left: 10px;
        width:100%;
        font-family: arial;
        text-decoration: none;
        overflow: hidden;
    }

Answer 1

When a menu is open, set position: fixed on the body, and remove on close.

 .fixed-position {
    position: fixed;
 }

 if ($('#mob-menu').is(':visible')) {
    $('body').addClass("fixed-position");
 } else {
    $('body').removeClass("fixed-position");
 }