JavaScript dynamic array with object and array

Question

I have a problem with creating list with objects in JavaScript: the object is going to contain an Integer value and an array.

The structure will look like this (this code works):

var list = [ {
            id : 1234,
            dependencyList : [ {
                id : 2142
            }, {
                id : 5313
            } ]
        }, {
            id : 4312,
            dependencyList : [ {
                id : 2142
            }, {
                id : 5313
            } ]
        } ];

The problem is that I want to create this list dynamically, in other words something like this:

var list = [];

var object;
object.id=1234;
object.dependencyList = [];
object.dependencyList.push(2222);

list.push(object);

This code does not work when I try to alert(list[0].length) and it returns 0 and after using JSON.stringify(list) it only returns [[]].

Anyone know a solution for this?

list[0] is object not an array, in your sample list[0] == { id : 1234, dependencyList : [ { id : 2142 }, { id : 5313 } ] } — Grundy
– Grundy, Commented Nov 15, 2013 at 15:00
Unrelated: Seems to me that your list could look better as a map of arrays: list = { 1234 : [ 2142, 5313], 4312 : [2142, 5313] }; — Tibos
– Tibos, Commented Nov 15, 2013 at 15:06

Vivin Paliath · Accepted Answer · 2013-11-15 15:03:31Z

1

list[0] is an object and not an array, which is why you're not seeing anything for length. Try:

console.log(Object.keys(list[0]).length);

Or you could even just console.log(list[0]) and check your console to ensure that it contains something.

Also, I assume you meant:

var object = {};

Because otherwise object is undefined and your script won't work. Another thing you will have to change is:

object.dependencyList.push(2222);

to:

object.dependencyList.push({id: 2222});

answered Nov 15, 2013 at 15:03

Vivin Paliath

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3 Comments

dag roger stokland rui Over a year ago

var list = []; var object = {}; object.id=4444; object.dependencyList = []; object.dependencyList.push({id:2222}); list.push(object);

Rob Baillie Over a year ago

@dag-roger-stokland-rui Not sure why this isn't voted as the answer, though the one that contains half of this answer is...

dag roger stokland rui Over a year ago

Yes, i agree. This answer is more detailed.

will.ogden · Accepted Answer · 2013-11-15 15:04:00Z

1

Object isn't defined. Do:

var object = {};

answered Nov 15, 2013 at 15:04

will.ogden

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1 Comment

Rob Baillie Over a year ago

Though be aware the structure won't be the same as the one you describe, it'll be var list = [ { id : 1234, dependencyList : [ 2142, 5313 ] }, { id : 4312, dependencyList : [ 2142, 5313 ] } ];

Aguardientico · Accepted Answer · 2013-11-15 15:02:54Z

0

You should do list[0].dependencyList.length) also you shoud change: object.dependencyList.push(2222); for object.dependencyList.push({id: 2222});

answered Nov 15, 2013 at 15:02

Aguardientico

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Comments

Rob Baillie · Accepted Answer · 2013-11-15 15:20:54Z

Objects are your friend.

If you need to create a lot of these things, you should probably define how they are shaped in a function. An advantage of this is that you can then create a setter for adding a dependency that hides the implementation as a push against a particular member variable.

Something like this:

function createObject( id ) {
    var object = {};
    object.id = id;
    return object;
}

function createObjectWithDependencies( id ) {
    var object = createObject( id );
    object.dependencyList = [];

    object.addDependency = function( dependentObject ) {
        object.dependencyList.push( dependentObject );
    }

    return object;
}

var list = [];

var object = createObjectWithDependencies( 1234 );
object.addDependency( createObject( 2142 ) );
object.addDependency( createObject( 5313 ) );
list.push( object );

var object = createObjectWithDependencies( 4312 );
object.addDependency( createObject( 2142 ) );
object.addDependency( createObject( 5313 ) );
list.push( object );

console.log( list );

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