JS generate random boolean

!Math.round(Math.random());

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If your project has lodash then you can:

_.sample([true, false])

Alternatively you can use your own sample function (source):

const sample = arr => arr[Math.floor(Math.random() * arr.length)];

You can compare Math.random() to 0.5 directly, as the range of Math.random() is [0, 1) (this means 'in the range 0 to 1 including 0, but not 1'). You can divide the range into [0, 0.5) and [0.5, 1).

var random_boolean = Math.random() < 0.5;


// Example
console.log(Math.random() < 0.1); //10% probability of getting true
console.log(Math.random() < 0.4); //40% probability of getting true
console.log(Math.random() < 0.5); //50% probability of getting true
console.log(Math.random() < 0.8); //80% probability of getting true
console.log(Math.random() < 0.9); //90% probability of getting true

For a more cryptographically secure value, you can use crypto.getRandomValues in modern browsers.

Sample:

var randomBool = (function() {
  var a = new Uint8Array(1);
  return function() {
    crypto.getRandomValues(a);
    return a[0] > 127;
  };
})();

var trues = 0;
var falses = 0;
for (var i = 0; i < 255; i++) {
  if (randomBool()) {
    trues++;
  }
  else {
    falses++;
  }
}
document.body.innerText = 'true: ' + trues + ', false: ' + falses;

Note that the crypto object is a DOM API, so it's not available in Node, but there is a similar API for Node.

Tags:

Javascript

Random

Boolean

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