如何Meteor.js随机提取数据？

Question

I tried to pick up data with random some like below but it seem picked up only a first one in database.

Template.miniSudoku.helpers({
    playGame: function(){
        var result = MiniSudoku.find({},{random:{$gte:Math.random()},limit:1});
        if (result === null) {
            var result = MiniSudoku.find({},{random:{$lte:Math.random()},limit:1});
        }
        return result;
    }
});

Answer 1

You have to use random as a selector, not as an option in the query, eg:

MiniSudoku.find({random: {$gte: Math.random()}}, {limit: 1});

Extra tips:

1. You could also rewrite this to MiniSudoku.findOne({random: {$gte: Math.random()}});

2. You shouldn't use var keyword when you assign a value second time.

3. You should assign Math.random() value to a variable, because in a corner case you can also get nothing from the second query :)

4. Selecting random document from Mongo can be tricky, as they don't support this out of the box like other databases do. You can vote for it at https://jira.mongodb.org/browse/SERVER-533