javascript - What is UInt8Array() max value? - Stack Overflow

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// Storing array and targeting HTML elements.
var array = new Uint8Array(1),
    output = document.getElementById('output'),
    btn = document.getElementById('btn');

btn.onclick = function() {
  // Get random values from the array.
  number = window.crypto.getRandomValues(array);
  // Show value on the front-end.
  output.innerHTML = number[0];
};

h1, button {
  text-align: center;
  font-family: sans-serif;
}

button {
  padding: 20px;
  display: block;
  margin: 0 auto;
  width: 175px;
  border: solid 5px #000;
  border-radius: 2px;
  background: none;
  font-size: 20px;
  cursor: pointer;
  text-transform: uppercase;
}

<h1 id="output">Click to go random.</h1>

<button id="btn">Randomize</button>

// Storing array and targeting HTML elements.
var array = new Uint8Array(1),
    output = document.getElementById('output'),
    btn = document.getElementById('btn');

btn.onclick = function() {
  // Get random values from the array.
  number = window.crypto.getRandomValues(array);
  // Show value on the front-end.
  output.innerHTML = number[0];
};

h1, button {
  text-align: center;
  font-family: sans-serif;
}

button {
  padding: 20px;
  display: block;
  margin: 0 auto;
  width: 175px;
  border: solid 5px #000;
  border-radius: 2px;
  background: none;
  font-size: 20px;
  cursor: pointer;
  text-transform: uppercase;
}

<h1 id="output">Click to go random.</h1>

<button id="btn">Randomize</button>

I've been experimenting with UInt8Array() method in Javascript to create random number. When used with window.crypto.getRandomValues(), it works even better than Math.random().

However I would like to know what's the max value this method could generate, so I was wondering if someone more experienced could give this information and perhaps explain me how this works and how this maximum value is defined. Also, can I use these numbers and store them in a variable?

• javascript
• ecmascript-6
• typed-arrays

Share Improve this question Follow edited Dec 16, 2015 at 21:32 csalmeida asked Mar 6, 2015 at 22:09 csalmeidacsalmeida 6281010 silver badges3030 bronze badges 3

• 1 I'm really curious and hope you'll answer this question: How in the world are you using a UInt8Array method to generate random numbers? That is some serious off-label use. – szupie Commented Mar 6, 2015 at 22:19
• 2 I was about to ask the same question, would you share a jsfiddle? – Gus Ortiz Commented Mar 6, 2015 at 22:19
• @szupie @Gus Ortiz I apologize, only now I've seen your questions. I've edited the question and added a jsfiddle as requested to explain that. Probably there are easier ways to do it but this is the way that I've found when I want a number bigger than 255. – csalmeida Commented Dec 16, 2015 at 21:35

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1 Answer 1

Sorted by: Reset to default 4

The definition of the method says:

The Uint8Array typed array represents an array of 8-bit unsigned integers. The contents are initialized to 0 ..

This means that the highest value is 2^8 - 1 meaning 255.

Calculated in JS as Math.pow(2, 8);

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