How to create an array with random values with the help of JavaScript ?

The task is to generate an array with random values with the help of JavaScript. There are two approaches which are discussed below:

Approach 1:

  • Use Math.random() and Math.floor() method to get the random values.
  • Push the values one by one in the array (But this approach may generate repeated values).

Example: This example implements the above approach.



filter_none

edit
close

play_arrow

link
brightness_4
code

<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        create an array with random values
    </title>
</head>
  
<body style="text-align:center;">
    <h1 style="color: green">  
        GeeksForGeeks  
    </h1>
    <p id="GFG_UP"></p>
    <button onclick="gfg_Run()">
        Click Here
    </button>
    <p id="GFG_DOWN" style="color:green;"></p>
  
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
        el_up.innerHTML = 
          "Click on the button to generate the array.";
  
        function gfg_Run() {
            el_down.innerHTML = Array.from({
                length: 10
            }, () => Math.floor(Math.random() * 10));
        }
    </script>
</body>
  
</html>

chevron_right


Output:

  • Before clicking on the button:
  • After clicking on the button:

Approach 2:

  • Create an array and put the values in it (like, 1 at index 0, 2 at index 1, 3 at index 2 in the same order by a loop.)
  • Assign variable (tp) = length of the array.
  • Run a loop on variable(tp).
  • Inside loop use Math.random() and Math.floor() method to get the random index of the array.
  • Swap this array value with the index(tp) and decrease the variable(tp) by 1.
  • Run the loop until variable(tp) becomes 0.

Example: This example implements the above approach.

filter_none

edit
close

play_arrow

link
brightness_4
code

<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        create an array with random values.
    </title>
</head>
  
<body style="text-align:center;">
    <h1 style="color: green">  
        GeeksForGeeks  
    </h1>
    <p id="GFG_UP"></p>
    <button onclick="gfg_Run()">
        Click Here
    </button>
    <p id="GFG_DOWN" 
       style="color:green;">
    </p>
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
        for (var a = [], i = 0; i < 10; ++i) a[i] = i;
  
        // Array like[1, 2, 3, 4, ...]
        el_up.innerHTML
          "Click on the button to generate the array.";
  
        function createRandom(arr) {
            var tmp, cur, tp = arr.length;
            if (tp)
  
                // Run until tp becomes 0.
                while (--tp) { 
  
                    // Generating the random index.
                    cur = Math.floor(Math.random() * (tp + 1)); 
  
                    // Getting the index(cur) value in variable(tmp).
                    tmp = arr[cur]; 
  
                    // Moving the index(tp) value to index(cur).
                    arr[cur] = arr[tp]; 
  
                    // Moving back the tmp value to
                    // index(tp), Swaping is done.
                    arr[tp] = tmp; 
                }
            return arr;
        }
  
        function gfg_Run() {
            el_down.innerHTML = createRandom(a);
        }
    </script>
</body>
  
</html>

chevron_right


Output:

  • Before clicking on the button:
  • After clicking on the button:


My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.