How to generate random value using Window.crypto getRandomValues()

by Anish

Posted on Sunday september 11, 2018

This sample chapter extracted from the book, Cryptography for JavaScript Developers.

The Window.crypto read-only property returns the Crypto object associated to the global object. This object allows web pages access to certain cryptographic related services.

Using the Window.crypto property to access the getRandomValues() method.

The Javascript Code

<script>
genRandomNumbers = function getRandomNumbers() {
  if (window.crypto || window.msCrypto) 
  {
  var array = new Uint32Array(10);
  window.crypto.getRandomValues(array);
 
  var randText = document.getElementById("myRandText");
  randText.innerHTML = "The random numbers are: "
  for (var i = 0; i < array.length; i++) {
    randText.innerHTML += array[i] + " \n";
  }
} 
    else throw new Error("Your browser can't generate secure random numbers");
}
</script>

The Html

<p id="myRandText">The random numbers are: </p>
<button type="button" onClick='genRandomNumbers()'>Generate 10 random numbers</button>

The Result

The random numbers are:

Broswer Support for window.crypto

The following browser has the support of window.crypto

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