How to get random elements from an array [duplicate]

Answer 1

//return a random integer between 0 and 10

document.write(Math.floor(Math.random()*11));

Answer 2

You could shuffle the array and pick the first four.

numbers.sort( function() { return 0.5 - Math.random() } );

Now numbers[0], numbers[1]... and so on have random and unique elements.

Note that this method may not be an optimal way to shuffle an array: see Is it correct to use JavaScript Array.sort() method for shuffling? for discussion.

Answer 3

If you want this to be as random as the native implementations of JavaScript's Math.random() will allow, you could use something like the following, which also has the advantages of leaving the original array untouched and only randomizing as much of the array as required:

function getRandomArrayElements(arr, count) {
    var shuffled = arr.slice(0), i = arr.length, min = i - count, temp, index;
    while (i-- > min) {
        index = Math.floor((i + 1) * Math.random());
        temp = shuffled[index];
        shuffled[index] = shuffled[i];
        shuffled[i] = temp;
    }
    return shuffled.slice(min);
}


var numbers = ['1','2','4','5','6','7','8','9','10'];
alert( getRandomArrayElements(numbers, 4) );

Answer 4

var numbers = new Array('1','2','4','5','6','7','8','9','10');
document.write(numbers[Math.floor(Math.random()*numbers.length)]);