Get a random item from a JavaScript array [duplicate]

Answer 1

1. solution: define Array prototype

Array.prototype.random = function () {
  return this[Math.floor((Math.random()*this.length))];
}

that will work on inline arrays

[2,3,5].random()

and of course predefined arrays

list = [2,3,5]
list.random()

2. solution: define custom function that accepts list and returns element

get_random = function (list) {
  return list[Math.floor((Math.random()*list.length))];
} 

get_random([2,3,5])

Answer 2

Use underscore (or loDash :)):

var randomArray = [
   '#cc0000','#00cc00', '#0000cc'
];

// use _.sample
var randomElement = _.sample(randomArray);

// manually use _.random
var randomElement = randomArray[_.random(randomArray.length-1)];

Or to shuffle an entire array:

// use underscore's shuffle function
var firstRandomElement = _.shuffle(randomArray)[0];

Answer 3

Here's yet another way:

function rand(items) {
    // "~~" for a closest "int"
    return items[~~(items.length * Math.random())];
}

Or as recommended below by @1248177:

function rand(items) {
    // "|" for a kinda "int div"
    return items[items.length * Math.random() | 0];
}

Answer 4

// 1. Random shuffle items
items.sort(function() {return 0.5 - Math.random()})

// 2. Get first item
var item = items[0]

Shorter:

var item = items.sort(function() {return 0.5 - Math.random()})[0];

Answer 5

var random = items[Math.floor(Math.random()*items.length)]

Answer 6

If you are using node.js, you can use unique-random-array. It simply picks something random from an array.