how to hand code an array into a JSON string?

Question

I need to write a JSON string that will be interpreted as an array, but only certain indexes will actually have any values.

I would like an array that looks like this:

array[1] = ["foo", "bar"]
array[5] = ["things", "stuff"]
array[37] = ["etc"];

So that to return "stuff" I could call array[5][1].

The catch is that not everything will have values, and I'm writing this string by hand, so I don't really want to start from 0 and do all the empty values. Is there an easy way to do this?

If you don't want to sart from 0, then array[5][1] should return "things" in your example, right? I don't think this can be achieved by using a pure json object. — martincho
– martincho, Commented Aug 30, 2011 at 19:43
possible duplicate of How to represent a sparse array in JSON? — James Montagne
– James Montagne, Commented Aug 30, 2011 at 19:43
Thanks, kingjiv, I didn't know the term "sparse array", so I was having trouble finding relevant results. Martin, the highest level of the array is the only one I care about. — Chris Sobolewski
– Chris Sobolewski, Commented Aug 30, 2011 at 19:45

65Fbef05 · Accepted Answer · 2011-08-30 20:22:51Z

5

JSON representation of your data structure...

var data = {"1":{"0":"foo","1":"bar"},"5":{"0":"things","1":"stuff"},"37":{"0":"etc"}};

or just...

var data = {"1":["foo","bar"],"5":["things","stuff"],"37":["etc"]};

edited Aug 30, 2011 at 20:22

answered Aug 30, 2011 at 19:47

65Fbef05

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2 Comments

Patrick Perini Over a year ago

tho, he wants numerical indices, so maybe var data = {1: ["foo", "bar"], 5: ["things", "stuff"], 37: ["etc"]};

gion_13 Over a year ago

the javascript object's keys are string. check it out yourself: a={1:'numeric',"1":'string'};alert(a[1]);

Rick · Accepted Answer · 2011-08-30 22:36:26Z

3

If by "JSON string", you actually meant "object literal", then this answer will be useless. If you actually meant "JSON string", then all you need to do is create a string that can be parsed by JSON.parse() that has all of the characteristics of a sparse array and place your sub arrays at the positions in which you need them (by whatever means you are creating the string in the first place). Take a look at this example:

var array, 
    json = '[ null, ["foo", "bar"], null, null, null, ["things", "stuff"], ' + 
            'null, null, null, null, null, null, null, null, null, null, ' + 
            'null, null, null, null, null, null, null, null, null, null, ' + 
            'null, null, null, null, null, null, null, null, null, null, ' + 
            'null, ["etc"]  ]';


array = JSON.parse( json );

console.log(
    array[ 1 ][ 1 ] // "bar"
);

console.log(
    array[ 5 ][ 1 ] // "stuff"
);

console.log(
    array[ 37 ][ 0 ] // "etc"
);

See also: http://jsfiddle.net/rwaldron/DWCEb/

Edit. As a final note, considering your statement "The catch is that not everything will have values, and I'm writing this string by hand, so I don't really want to start from 0 and do all the empty values. Is there an easy way to do this?"

The answer is: No. You cannot have your cake and eat it, too.

If you have the means to create the array with code first, then you could easily do:

var array = [];

array[1] = ["foo", "bar"];
array[5] = ["things", "stuff"];
array[37] = ["etc"];

console.log(
    JSON.stringify( array )
);

See also: http://jsfiddle.net/rwaldron/RJHEp/

edited Aug 30, 2011 at 22:36

answered Aug 30, 2011 at 19:58

Rick

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9 Comments

gion_13 Over a year ago

in order to imitate the real js response, you should probably change the nulls to undefined

65Fbef05 Over a year ago

Why define all the empty keys as null or undefined in the first place when you can explicitly define the keys: var json = '{"1":["foo","bar"],"5":["things","stuff"],"37":["etc"]}';

Rick Over a year ago

@65Fbef05 because the OP did not ask for JSON string that would be interpreted as an object... "I need to write a JSON string that will be interpreted as an array". The null and/or undefined "holes" are used to simulate a sparse array. See also: en.wikipedia.org/wiki/Sparse_array

65Fbef05 Over a year ago

Arrays are objects in Javascript. JSON.parse() returns an object.

Rick Over a year ago

@gion_13 Please see the live example I've just added.

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