Meteor sort collection random - sorting

Question

I want to get a randomly sorted set from a Meteor collection. What is the best/most efficient way?
Mongo options are controversial.
I am currently using underscore _.shuffle which is quite neat, eg:
Template.userList.helpers({
users: function() {
return _.shuffle(Meteor.users.find().fetch());
}
});
I use Jade, so maybe there's an option at the templating level?

Answer 1

You could use Lodash _.shuffle, like so:
Template.userList.helpers({
users: function() {
return _.shuffle(Meteor.users.find().fetch());
}
});
As hilarious as that might seem, there is a difference under the hood:
Underscore (source)
_.shuffle = function(obj) {
var set = isArrayLike(obj) ? obj : _.values(obj);
var length = set.length;
var shuffled = Array(length);
for (var index = 0, rand; index < length; index++) {
rand = _.random(0, index);
if (rand !== index) shuffled[index] = shuffled[rand];
shuffled[rand] = set[index];
}
return shuffled;
};
Lo-Dash (slightly modified for ease of comparison, source)
_.shuffle = function(collection) {
MAX_ARRAY_LENGTH = 4294967295;
return sampleSize(collection, MAX_ARRAY_LENGTH);
}
function sampleSize(collection, n) {
var index = -1,
result = toArray(collection),
length = result.length,
lastIndex = length - 1;
n = clamp(toInteger(n), 0, length);
while (++index < n) {
var rand = baseRandom(index, lastIndex),
value = result[rand];
result[rand] = result[index];
result[index] = value;
}
result.length = n;
return result;
}
You can take a look at this SO discussion for a more in-depth look at comparing the two libraries.
Both, Underscore and Lo-Dash, use the Fisher-Yates shuffle which you'd have a hard time doing "better" than.