Initializing a 'multidimensional' object in javascript

Question

I'm having an issue with trying to populate a multidimensional object in javascript before all of the dimensions are defined.

For example this is what I want to do:

var multiVar = {};
var levelone = 'one';
var leveltwo = 'two';

multiVar[levelone][leveltwo]['levelthree'] = 'test'

It would be extremely cumbersome to have to create each dimension with a line like this:

var multiVar = {};

multiVar['levelone'] = {};
multiVar['levelone']['leveltwo'] = {};
multiVar['levelone']['leveltwo']['levelthree'] = 'test'

The reason why I need to do it without iterative priming is because I don't know how many dimensions there will be nor what the keys it will have. It needs to be dynamic.

Is there a way to do that in a dynamic way?

I don't understand what you're trying to do. What is this for? How will you fill it? Can you give an example of a filled in object? — Peter Ajtai
– Peter Ajtai, Commented Oct 9, 2011 at 2:16
I'm using it for JSON data being returned back from a server for Yahoo Fantasy Football league data... — Austin
– Austin, Commented Oct 9, 2011 at 2:25
What exactly are you trying to do with this JSON that you need this? — Matt Ball
– Matt Ball, Commented Oct 9, 2011 at 2:41

Matt Ball · Accepted Answer · 2011-10-09 02:45:26Z

4

You could write a function which ensures the existence of the necessary "dimensions", but you won't be able to use dot or bracket notation to get this safety. Something like this:

function setPropertySafe(obj)
{
    function isObject(o)
    {
        if (o === null) return false;
        var type = typeof o;
        return type === 'object' || type === 'function';
    }

    if (!isObject(obj)) return;

    var prop;
    for (var i=1; i < arguments.length-1; i++)
    {
        prop = arguments[i];
        if (!isObject(obj[prop])) obj[prop] = {};
        if (i < arguments.length-2) obj = obj[prop];
    }

    obj[prop] = arguments[i];
}

Example usage:

var multiVar = {};
setPropertySafe(multiVar, 'levelone', 'leveltwo', 'levelthree', 'test');
/*
multiVar = {
    levelone: {
        leveltwo: {
            levelthree: "test"
        }
    }
}
*/

edited Oct 9, 2011 at 2:45

answered Oct 9, 2011 at 2:20

Matt Ball

361k102 gold badges655 silver badges725 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Christian C. Salvadó Over a year ago

Note that your isObject function will return true for isObject(null) and it will return false if you pass a function object, both cases could give you problems.

Matt Ball Over a year ago

It works now. It could probably be done more elegantly using recursion but I'll leave that as an "exercise to the reader." ;-)

Collectives™ on Stack Overflow

Initializing a 'multidimensional' object in javascript

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related