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How to store JavaScript functions in a queue and execute in that order?
  • Last Updated : 15 Jul, 2020
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The task is to execute the functions in the order defined in the queue with the help of JavaScript. There are two approaches that are discussed below.

Approach 1: Declare the functions and use array push() method to push the functions in the array. Later traverse the array and execute the functions one by one.

  • Example: This example implements the above approach.




    <!DOCTYPE html>
    <html>
        <head>
            <title>
                Store JavaScript functions in 
                a queue and execute in that order
            </title>
        </head>
        <body style="text-align: center;">
            <h1>
                GeeksforGeeks
            </h1>
            <p id="GFG_UP"></p>
            <button onclick="myGFG()">
                Click Here
            </button>
            <p id="GFG_DOWN"></p>
            <script>
                var up = document.getElementById("GFG_UP");
                up.innerHTML = 
                  "Click on the button to execute "+
                  "the function in order of queue";
                var down = document.getElementById("GFG_DOWN");
                function myGFG() {
                    
                    // First function
                    function function1() {
                        alert("First Function");
                    }
                    
                    // Second function
                    function function2() {
                        alert("Second Function");
                    }
                    var orderQueue = [];
                    
                    // Push them in queue
                    orderQueue.push(function1);
                    orderQueue.push(function2);
                    while (orderQueue.length > 0) {
                        // Execute in order
                        orderQueue.shift()();
                    }
                    down.innerHTML = 
                      "Functions executed in queue order";
                }
            </script>
        </body>
    </html>
  • Output:

Approach 2:Declare the functions and use arrayindexing to assign the functions to index of the array in the order. Later traverse the array and execute the functions one by one.

  • Example: This example implements the above approach.




    <!DOCTYPE html>
    <html>
        <head>
            <title>
                Store JavaScript functions in a 
                queue and execute in that order
            </title>
        </head>
        <body style="text-align: center;">
            <h1>
                GeeksforGeeks
            </h1>
            <p id="GFG_UP"></p>
            <button onclick="myGFG()">
                Click Here
            </button>
            <p id="GFG_DOWN"></p>
            <script>
                var up = document.getElementById("GFG_UP");
                up.innerHTML = 
                  "Click on the button to execute "+
                  "the function in order of queue";
                var down = document.getElementById("GFG_DOWN");
                function myGFG() {
                    
                    // First function
                    function function1() {
                        alert("First Function");
                    }
                    
                    // Second function
                    function function2() {
                        alert("Second Function");
                    }
                    var functions = new Array();
                    // Adding the functions in the order
                    // in queue(array)
                    functions[0] = function1;
                    functions[1] = function2;
                    for (var i = 0; i < functions.length; i++) {
                        
                        // Executing them in order.
                        functions[i].call();
                    }
                    down.innerHTML
                        "Functions executed in queue order";
                }
            </script>
        </body>
    </html>
  • Output:

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