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July 4, 2023 14:38
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Math.random() vs crypto.getRandomValues() Visual random generation values from different ways in Javascript
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<html> | |
<head> | |
<title>Math.random() vs crypto.getRandomValues()</title> | |
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> | |
<style> | |
body { background: #333; text-align: center; } | |
canvas { | |
margin: 50px; | |
height: 400px; | |
width: 400px; | |
background: black; | |
border: 1px solid black; | |
} | |
button { | |
text-align: center; | |
font-size: 24px | |
} | |
table { | |
color: #eee; | |
} | |
</style> | |
</head> | |
<body> | |
<table> | |
<tr> | |
<td colspan="2" style="text-align: center;"> | |
<button>Generate</button> | |
</td> | |
</tr> | |
<tr> | |
<td colspan="2" style="text-align: center;"> | |
Visual random generation values from different ways in Javascript | |
</td> | |
</tr> | |
<tr> | |
<td>Math.random()</td> | |
<td>crypto.getRandomValues()</td> | |
</tr> | |
<tr> | |
<td> | |
<canvas id="c1"></canvas> | |
</td> | |
<td> | |
<canvas id="c2"></canvas> | |
</td> | |
</tr> | |
</table> | |
<script> | |
const canvas1 = document.querySelector('#c1') | |
, canvas2 = document.querySelector('#c2') | |
, dpi = window.devicePixelRatio; | |
var size = 400; | |
function rescale(canvas) { | |
canvas.width = size * dpi; | |
canvas.height = size * dpi; | |
//canvas.style.width = size * dpi + "px"; | |
//canvas.style.height = size * dpi + "px"; | |
} | |
rescale(canvas1); | |
rescale(canvas2); | |
const context1 = canvas1.getContext('2d') | |
, context2 = canvas2.getContext('2d'); | |
const {width} = canvas1.getBoundingClientRect(); | |
function drawPix(x, y, context) { | |
context.fillStyle = '#fff'; | |
context.fillRect(x, y, 1, 1); | |
} | |
function getRnd(max) { | |
return Math.floor(Math.random() * max); | |
} | |
function getRandomInt (min, max) { | |
return Math.floor(Math.random() * (max - min + 1)) + min; | |
} | |
function getRndCrypt(max) { | |
// Create byte array and fill with 1 random number | |
var byteArray = new Uint8Array(1); | |
crypto.getRandomValues(byteArray); | |
var range = max + 1; | |
var max_range = 256; | |
if (byteArray[0] >= Math.floor(max_range / range) * range) | |
return getRnd(max); | |
return (byteArray[0] % range); | |
} | |
function clear() { | |
context1.clearRect(0, 0, width, width); | |
context2.clearRect(0, 0, width, width); | |
} | |
function draw() { | |
clear(); | |
const maxPix = Math.pow(width, 2); | |
for (let i=0; i < maxPix; i++) { | |
drawPix(getRnd(width), getRnd(width), context1) | |
drawPix(getRndCrypt(width), getRndCrypt(width), context2) | |
//console.log(getRnd(width), getRndCrypt(width)) | |
} | |
} | |
//setInterval(draw, 10) | |
//draw(); | |
document.querySelector('button').addEventListener('click', draw, false); | |
</script> | |
</body> | |
</html> |
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