JavaScript - How to generate Random number in a given Range

The Math.random() method in JavaScript generates a random number between 0 and 1. To generate a random number within a specific range, you need a different formula. Learn how to use Math.random() to create random numbers between any two values in JavaScript.

Try this.

Enter number range and click the "Generate Random Number" button.

Min.: Max.:

Math.random() function

First, lets check the Math.random() function.

<script>
  document.write (Math.random());  // Output: a random value between 0 and 1, such as, 0.7633
</script>

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To generate a random number between 0 and 10, you can use this formula.

<script>
  document.write (Math.random() * 10);  // Output: a random value like 4.805398688602722
</script>

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Now let us assume, I want to generate a random number between the range 5 and 10. I'll use this formula.

<script>
  let min = 5,
    max = 10;
  
  let rnd = Math.random() * (max - min) + min;
  document.write(Math.floor(rnd));     // Rounding off the value using Math.floor() function.
</script>

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I have defined the minimum and maximum numbers as variables. Using Math.random(), I generate a random number within this range. To round off the value, I use the Math.floor() function.

We can make it more dynamic by allowing users to input the min. and max. values. To do this, I am adding two textboxes.

<body>
  <p>Minimum: <input type='textbox' id='min'></p>
  <p>Maximum: <input type='textbox' id='max'></p>
  
  <p>
    <input type='button' value='Generate Random Number' onclick="generateRnd()">
  </p>
  
  <p id='result'></p>
</body>

<script>
  let generateRnd = () => {
    let min = Math.ceil(document.getElementById('min').value), 
    max = Math.floor(document.getElementById('max').value);
  
    let rnd = Math.random() * (max - min) + min;
    document.getElementById('result').innerHTML = Math.floor(rnd);
  }
</script>

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