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.
}

What is generating the JSON? Seems like it would be easier to randomize it at that point — Explosion Pills, Feb 04 '13 at 23:09
@explosion: I start coding, I write the 4000 lines lexical database by hand. No random function... yet ! — Hugolpz, Feb 04 '13 at 23:15

score 5 · Accepted Answer · edited May 23 '17 at 12:33

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)

I think I will need the keys. Indeed, I now need to grasp again my data > a random key > to pick the values I want. — Hugolpz, Feb 04 '13 at 23:33
rather than : var keyArray = $.map(data, function (value, key) { return key; }); Let's use : var keyArray = Object.keys(data); — Hugolpz, Feb 06 '13 at 22:12
I voted your answer up, but accepted my answer which I implemented in my code. (note: I get no point from accepting my own answer.) — Hugolpz, Feb 25 '13 at 10:18

score 3 · Answer 2 · edited May 23 '17 at 11:53

3

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.

edited May 23 '17 at 11:53

Community

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answered Feb 04 '13 at 23:14

Mario Corchero

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Mario, thanks again. Your comments were really adapted to the begginner I am, I was looking for a **shuffle** function indeed. – Hugolpz Feb 25 '13 at 14:16

score 0 · Answer 3 · answered Dec 22 '16 at 10:55

0

use the Object.keys function

var obj = { 0: 'a', 1: 'b', 2: 'c' };
console.log(Object.keys(obj)); // console: ['0', '1', '2']

more: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/keys

answered Dec 22 '16 at 10:55

KARTHIKEYAN.A

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

3 Answers3

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