node.js - Why JavaScript Math.random() returns same number multiple times

Question

I have an array with two items and I need to random a choice of this items but the most of times I get the same item from array...

See the code:

var numbers = Array(523,3452);
var choice = numbers[Math.floor(Math.random()*numbers.length)];
console.log("Choice:", choice);

How can I avoid this kind of behavior?

Answer 1

Random numbers can appear in streaks; that's part of being random. But over time the law of large numbers should take over and even out those streaks. You can test that easily enough by running this a bunch of times and counting:

var numbers = Array(523,3452);
let counts = [0,0]

for (let i = 0; i < 10000; i++) {
    let choice = numbers[Math.floor(Math.random()*numbers.length)];
    if (choice ===  523) counts[0]++
    else if (choice == 3452) counts[1]++
}

// counts should be about even
console.log(counts);