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How to generate a random boolean using JavaScript ?

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The task is to generate random boolean value. Here we are going to use JavaScript to achieve the goal.

Approach 1:

  • Calculate Math.random() function.
  • If it is less than 0.5, then true otherwise false.

Example 1: This example implements the above approach.




<!DOCTYPE HTML> 
<html
  
<head
    <title
        How to generate a random 
        boolean using JavaScript?
    </title>
</head
  
<body style = "text-align:center;" id = "body"
      
    <h1 id = "h1" style = "color:green;"
        GeeksForGeeks 
    </h1>
      
    <p id = "GFG_UP" style
        "font-size: 15px; font-weight: bold;">
    </p>
      
    <button onclick = "gfg_Run()"
        Click here
    </button>
      
    <p id = "GFG_DOWN" style
        "font-size: 23px; font-weight: bold; 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 random boolean.";
          
        function gfg_Run() {
            el_down.innerHTML = Math.random() >= 0.5;
        }         
    </script
</body
  
</html>

Output:

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

Approach 2:

  • Create an array containing ‘true’ and ‘false’ values.
  • Calculate Math.random() and round its value.
  • Use rounded value as the index to the array, to get boolean.

Example 2: This example implements the above approach.




<!DOCTYPE HTML>  
<html>  
  
<head
    <title
        How to generate a random
        boolean using JavaScript?
    </title>
</head
  
<body style = "text-align:center;" id = "body">  
      
    <h1 id = "h1" style = "color:green;" >  
        GeeksForGeeks  
    </h1>
      
    <p id = "GFG_UP" style
            "font-size: 15px; font-weight: bold;">
    </p>
      
    <button onclick = "gfg_Run()"
        Click here
    </button>
      
    <p id = "GFG_DOWN" style
        "font-size: 23px; font-weight: bold; color: green; ">
    </p>
      
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
        var ar = [true, false];
          
        el_up.innerHTML = "Click on the button to "
                        + "generate random boolean.";
      
        function gfg_Run() {
            var index = Math.round(Math.random());
            el_down.innerHTML = ar[index];
        }         
    </script
</body>  
  
</html>

Output:

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

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Last Updated : 12 Sep, 2019
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