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How to prevent Body from scrolling when a modal is opened using jQuery ?

  • Last Updated : 12 Jan, 2021

Given an HTML document with a modal, the task is to prevent the body element from scrolling whenever the modal is in an open state. This task can be easily accomplished using JavaScript.

Approach: A simple solution to this problem is to set the value of the “overflow” property of the body element to “hidden” whenever the modal is opened, which disables the scroll on the selected element. Once the modal is closed, we would set the “overflow” property of the body element to “auto” so that scroll functionality is enabled on the body element. To find out whether the modal is opened or not, we would check if it has the “hidden” CSS class in its class list using the classList.contains() method of JavaScript. This “hidden” class is responsible for the opening and closing (changing display property) of the modal on a button click. Check out the given example for a better understanding. 

Example:

HTML




<!DOCTYPE html>
<html lang="en">
  
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content=
        "width=device-width, initial-scale=1.0" />
  
    <style>
        body {
            padding: 5% 20%;
        }
  
        #container {
            z-index: 1;
        }
  
        #btn {
            border: none;
            font-size: 24px;
            padding: 12px 36px;
            color: white;
            background-color: green;
        }
  
        #modal {
            height: 200px;
            width: 400px;
            padding: 60px;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            z-index: 999;
            background-color: green;
            color: white;
        }
  
        .hidden {
            display: none;
        }
    </style>
</head>
  
<body>
  
    <!--Button to toggle modal-->
    <button id="btn" onclick="showModal()">
        Toggle modal
    </button>
  
    <!--Modal container-->
    <div id="modal" class="hidden">
        <div id="modal-body">
            <h1>GeeksforGeeks</h1>
            <h2>This is a modal</h2>
        </div>
    </div>
  
    <!--Long text so that the body scrolls-->
    <div id="container">
        <h1>
            Given a graph and a source vertex in 
            the graph, find shortest paths from 
            source to all vertices in the given 
            graph. Dijkstra’s algorithm is very 
            similar to Prim’s algorithm for minimum
            spanning tree. Like Prim’s MST, we 
            generate a SPT (shortest path tree) 
            with given source as root.
            We maintain two sets, one set contains 
            vertices included in shortest path tree,
            other set includes vertices not yet 
            included in shortest path tree. At every
            step of the algorithm, we find a vertex 
            which is in the other set (set of not yet
            included) and has a minimum distance from
            the source. Below are the detailed steps
            used in Dijkstra’s algorithm to find the
            shortest path from a single source vertex
            to all other vertices in the given graph.
            Algorithm Create a set sptSet (shortest 
            path tree set) that keeps track of vertices
            included in shortest path tree, i.e., whose
            minimum distance from source is calculated 
            and finalized. Initially, this set is empty.
            Assign a distance value to all vertices in 
            the input graph. Initialize all distance 
            values as INFINITE.
            Assign distance value as 0 for the source 
            vertex so that it is picked first. While 
            sptSet doesn’t include all vertices Pick a 
            vertex u which is not there in sptSet and 
            has minimum distance value. Include u to 
            sptSet. Update distance value of all adjacent 
            vertices of u. To update the distance values,
            iterate through all adjacent vertices. For 
            every adjacent vertex v, if sum of distance 
            value of u (from source) and weight of edge 
            u-v, is less than the distance value of v,
            then update the distance value of v.
  
            Given a graph and a source vertex in the 
            graph, find shortest paths from source to
            all vertices in the given graph. Dijkstra’s 
            algorithm is very similar to Prim’s 
            algorithm for minimum spanning tree.
            Like Prim’s MST, we generate a SPT (shortest 
            path tree) with given source as root.
            We maintain two sets, one set contains 
            vertices included in shortest path tree, 
            other set includes vertices not yet included
            in shortest path tree.
            At every step of the algorithm, we find a 
            vertex which is in the other set (set of not 
            yet included) and has a minimum distance 
            from the source.
  
            Below are the detailed steps used in 
            Dijkstra’s algorithm to find the shortest 
            path from a single source vertex to all other 
            vertices in the given graph. Algorithm
            Create a set sptSet (shortest path tree set) 
            that keeps track of vertices included in 
            shortest path tree, i.e., whose minimum 
            distance from source is calculated and 
            finalized. Initially, this set is empty. Assign 
            a distance value to all vertices in the input 
            graph. Initialize all distance values as INFINITE.
            Assign distance value as 0 for the source 
            vertex so that it is picked first. While sptSet 
            doesn’t include all vertices Pick a vertex u 
            which is not there in sptSet and has minimum 
            distance value. Include u to sptSet.
            Update distance value of all adjacent vertices 
            of u. To update the distance values, iterate 
            through all adjacent vertices. For every 
            adjacent vertex v, if sum of distance value 
            of u (from source) and weight of edge u-v, 
            is less than the distance value of v, then 
            update the distance value of v.
        </h1>
    </div>
  
    <script>
          
        // Select required elements from the DOM
        const modal = document.querySelector("#modal");
        const body = document.querySelector("body");
  
        const showModal = function (e) {
            modal.classList.toggle("hidden");
  
            if (!modal.classList.contains("hidden")) {
                // Disable scroll
                body.style.overflow = "hidden";
            } else {
                // Enable scroll
                body.style.overflow = "auto";
            }
        };
    </script>
</body>
  
</html>

Output:

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