How to get a random element from an array

Short answer

Multiply Math.random() by the length and round down to get a valid index:

const colors = ['red', 'green', 'blue'];
const color = colors[Math.floor(Math.random() * colors.length)];
 
console.log(colors.includes(color));

Output:

true

Several without repeats

Shuffle a copy of the array and take the first elements:

const shuffle = (array) => {
  const copy = [...array];
  for (let i = copy.length - 1; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    [copy[i], copy[j]] = [copy[j], copy[i]];
  }
  return copy;
};
 
const winners = shuffle(['Anna', 'Oleg', 'Maria', 'Ivan', 'Olga']).slice(0, 2);
 
console.log(winners.length, new Set(winners).size);

Output:

2 2

Common mistake

Math.round() instead of Math.floor() sometimes gives an index equal to the length, and the result is undefined:

const colors = ['red', 'green', 'blue'];
 
console.log(colors[Math.round(0.9 * colors.length)]);

Output:

undefined

Thanks for reading!

Short answer

Several without repeats

Common mistake

Functions used in this recipe

Thanks for reading!