This question already has answers here: Getting a random value from a JavaScript array (27 answers) Closed 7 years ago.
var items = Array(523, 3452, 334, 31, ..., 5346);
How do I get random item from items
?
var item = items[Math.floor(Math.random()*items.length)];
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];
_.sample([1, 2, 3, 4, 5, 6])
sample
function if you want: npmjs.com/package/lodash.sample
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
var list = [2,3,5]
list.random()
2. solution: define custom function that accepts list and returns element
function get_random (list) {
return list[Math.floor((Math.random()*list.length))];
}
get_random([2,3,5])
ns.
or ns_
format where applicable.
for (let i in arr)
loop, it iterates all the expected indexes, and also iterates an index of "rand". Had to switch to a for (let i=0,l=arr.length;i<l;i++)
loop to fix it.
If you really must use jQuery to solve this problem (NB: you shouldn't):
(function($) {
$.rand = function(arg) {
if ($.isArray(arg)) {
return arg[$.rand(arg.length)];
} else if (typeof arg === "number") {
return Math.floor(Math.random() * arg);
} else {
return 4; // chosen by fair dice roll
}
};
})(jQuery);
var items = [523, 3452, 334, 31, ..., 5346];
var item = jQuery.rand(items);
This plugin will return a random element if given an array, or a value from [0 .. n) given a number, or given anything else, a guaranteed random value!
For extra fun, the array return is generated by calling the function recursively based on the array's length :)
Working demo at http://jsfiddle.net/2eyQX/
$
in the usage line with jQuery
.
$
is not being used at least once per each line, therefore it does not have enough jQuery.
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];
}
~~
? Never seen that in JS before.
Math.floor
.
items[items.length * Math.random() | 0]
:)
var random = items[Math.floor(Math.random()*items.length)]
jQuery is JavaScript! It's just a JavaScript framework. So to find a random item, just use plain old JavaScript, for example,
var randomItem = items[Math.floor(Math.random()*items.length)]
// 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];
Even shoter (by José dB.):
let item = items.sort(() => 0.5 - Math.random())[0];
items[1]
is the second item, the first is items[0]
.
let item = items.sort(() => 0.5 - Math.random())[0];
var rndval=items[Math.floor(Math.random()*items.length)];
var items = Array(523,3452,334,31,...5346);
function rand(min, max) {
var offset = min;
var range = (max - min) + 1;
var randomNumber = Math.floor( Math.random() * range) + offset;
return randomNumber;
}
randomNumber = rand(0, items.length - 1);
randomItem = items[randomNumber];
credit:
Javascript Function: Random Number Generator
Math.floor(Math.random() * (max - min + 1)) + min
If you are using node.js, you can use unique-random-array. It simply picks something random from an array.
An alternate way would be to add a method to the Array prototype:
Array.prototype.random = function (length) {
return this[Math.floor((Math.random()*length))];
}
var teams = ['patriots', 'colts', 'jets', 'texans', 'ravens', 'broncos']
var chosen_team = teams.random(teams.length)
alert(chosen_team)
Array.random
by the client that behaves differently than yours, breaking future code. You could at least check to make sure it doesn't exist before adding it.
const ArrayRandomModule = {
// get random item from array
random: function (array) {
return array[Math.random() * array.length | 0];
},
// [mutate]: extract from given array a random item
pick: function (array, i) {
return array.splice(i >= 0 ? i : Math.random() * array.length | 0, 1)[0];
},
// [mutate]: shuffle the given array
shuffle: function (array) {
for (var i = array.length; i > 0; --i)
array.push(array.splice(Math.random() * i | 0, 1)[0]);
return array;
}
}
Success story sharing
undefined
error.var items = ["a","e","i","o","u"]
var objResults = {}
for(var i = 0; i < 1000000; i++){
var randomElement = items[Math.floor(Math.random()*items.length)]
if (objResults[randomElement]){
objResults[randomElement]++
}else{
objResults[randomElement] = 1
}
}
console.log(objResults)
The results are pretty randomized after 1000000 iterations:Object {u: 200222, o: 199543, a: 199936, e: 200183, i: 200116}
Math.round
is not a valid substitution forMath.floor
. Usinground
would cause accidentally referencing an undefined index, say in the caseMath.random()
is 0.95 anditems.length
is 5.Math.round(0.95*5)
is 5, which would be an invalid index.floor(random)
will always be zero in your example.items[items.length * Math.random() | 0]
:)