How to retrieve random JSON object by key from JSON dictionary?

Question

I have a JSON object which consists of a long list of other JSON objects which have some common properties to each other such :

var myData = { 
    "0291" : { "Firstname" : "Jeremy", "Surname" : "Dyson" },
    "0398" : { "Firstnname" : "Billy", "Surname" : "Bunter" },
    "6714" : { "Firstnname" : "Harry", "Surname" : "Peterson" },
    "9080" : { "Firstnname" : "Barry", "secondname": "Joe", "Surname" : "Mainwaring"}
    ...
    ...
}

I already built an html template. With the JS, I want to pick or iterate (random pick + loop) through the objects in data{} in random order, so I can fill up the HTML on the fly for each visitor. The random part is important, so each visitor likely get a different data.

Plain JavaScript or jQuery solutions will work in the context in which this is being deployed.

---

EDIT: Solution I implemented is below.

1. Collect all keys :

var keyArray = Object.keys(myData);

2. Shuffle function:

function shuffle(o){ //v1.0
    for(var j, x, i = o.length; i; j = parseInt(Math.random() * i), x = o[--i], o[i] = o[j], o[j] = x);
    return o;
};
keyArray = shuffle(keyArray); // shuffle it!

3. Loop to iterate:

for (var i = 0; i < keyArray.length; ++i) {
    var current = data[keyArray[i]];
    ... // what you want to do each time.
}

Answer 1

First, convert the data object to an array (the keys on the first level will be lost), like shown here: https://stackoverflow.com/a/11474071/664108

var dataArray = $.map(data, function (value, key) { return value; });

Then shuffle the array (see How to randomize (shuffle) a JavaScript array?)

Alternatively you could just shuffle the keys and then operate on the original object. This way you also have still the keys:

var keyArray = $.map(data, function (value, key) { return key; });

shuffle(keyArray); // example (shuffle function has to be implemented, see above)

for (var i = 0; i < keyArray.length; ++i) {
    var current = data[keyArray[i]];
    // do stuff with current dataset
}

Addition from the comments

the key array can also be created by:

var keyArray = Object.keys(data);

But note that this only works on modern browsers, you should not use it if you want to support Internet Explorer in versions up to IE 8 (see: http://msdn.microsoft.com/en-us/library/ie/ff688127(v=vs.94).aspx)

Answer 2

Have you think about generating the JSON randomly already or shufflng it? Shuffle in Javascript

If you shuffle the array, you can apply foreach and you get the items in a random order. :)

Note: It might be faster to shuffle just a copy of the IDs.

Disclaimer! I asuumed that for your case you need just Pseudorandomness.