Pushing to array

Question

I need to loop through array and each array in array that has extra values, push them to their parent array as separate item. I hope this makes sense..

This is the structure of my initial array:

{type:
    [ 0:
        value: "tomato"
    ],
    [ 1:
        {value: "apple",
        [ extras:
           [ 0: { value: "green" } ],
           [ 1: { value: "red" } ]
        ]
    ],
    [ 2:
        value: "pineapple"
    ]
}

What the result would have to look like:

[type:
    [ 0:
        tomato
    ],
    [ 1:
        apple,
        green,
        red
    ],
    [ 2:
        pineapple
    ]
]

What I've tried and failed: (I also commented the error I get on right line)

var response = /* json of first codeblock in question is response from ajax */;

var items = JSON.parse( response );

var type = Object.keys( items )[0];

var myArray = [] 
var count = items[type].lenght;

//Loop through main items in "type"
for( i = 0; i < count; i++ ) {

    var value = items[type][i][value]; 
    myArray[type][i] = [value];  //Uncaught TypeError: Cannot set property '0' of undefined 

    if( items[type][i][extras] ) {

        var extracount = items[type][i][extras].lenght;

        //Loop through extras
        for( k = 0; k < extracount; k++ ) {

            var extra = items[type][i][extras][k][value];
            myArray[type][i].push( extra );
        }
    }     
}

My main problem that I don't understand and that seems to be the problem in my example as well:

If I declare an empty array, how do I:

push an item to that array also declaring a new array around that item?
push another item to that array that was made around the first item?

No, it doesn't makes any sense. You should read more about javascript objects and arrays before doing this. Someone can write the code for you, but you won't learn a thing from it. Your arrays are simply wrong. Anyway, you should explain the expected behavior — Frondor, Jan 18 '16 at 18:33
@Frondor I disagree - I would learn a lot from this.. and I did my research but I didn't find any good reference for this exact problem. `myArray[type] = [value];` works perfectly but `myArray[type][i] = [value];` doesn't.. Same thing with `push()`. — Solo, Jan 18 '16 at 18:35
You cannot add indexes into JavaScript arrays. Use objects for those purposes, but as @Frondor said, learn and read more about JavaScript before doing anything. — Zlatan Omerović, Jan 18 '16 at 18:35
Yes, you are attempting to use and create associative arrays, which are just objects with named properties in javascript. — Kevin Lee, Jan 18 '16 at 18:36
If you need associative array, you'll have to use Objects, the Javascript array is restricted to only numeric ordered keys and values. — Edson Horacio Junior, Jan 18 '16 at 18:38
And the code you posted doesn't say anything, because some essential parts are missing, `items` array. — Frondor, Jan 18 '16 at 18:39
@Solo The most important part is still missing, the CONTENT of `items`. Consider "hardcoding" an sample `response`. And please, always explain what you want to do, or what you intend to do with it — Frondor, Jan 18 '16 at 18:42

score 1 · Accepted Answer · answered Jan 18 '16 at 18:57

This is what I believe you want. The following code may be incorrect, because I'm approximating what I believe your items object contains.

var items = {
    type: [
        {
            value: "tomato"
        },
        {
            value: "apple",
            extras: [
                {
                    value: "green"
                }, {
                    value: "red"
                }
            ]
        },
        {
            value: "pineapple"
        }
    ]
};
var myArray = {
    type: []
};


var count = items['type'].length;

//Loop through main items in "type"
for (i = 0; i < count; i++) {

    var subarray = [];
    subarray.push(items['type'][i]['value']);

    if (items['type'][i]['extras']) {
        var extracount = items['type'][i]['extras'].length;
        //Loop through extras
        for (k = 0; k < extracount; k++) {

            var extra = items['type'][i]['extras'][k]['value'];
            subarray.push(extra);
        }
    }
    myArray['type'].push(subarray);
}

Some notes:

You will definitely need to learn the difference between an array and an object in javascript. There are plenty of resources online for this.

When retrieving/manipulating a property prop from an object obj (i.e. for a key-value pair), you will need to use obj.prop or obj['prop']. Note the use of a string in the latter example.

For an array arr, you should use arr.push(value) to push a new value onto the array.

Thanks for answering. I normally know the difference between these two but it gets complicated when object contains several arrays that contains arrays and objects _etc_. Then it gets confusing how does the selection look like and when to use `push()` or something else. — Solo, Jan 18 '16 at 19:00
A quick way to debug your variables is to create a breakpoint in your code in Developer Tools (or your browser's equivalent) or to use `console.log(items)`. You'll be able to view the contents of the variable, and determine the type (array or object, in this example) of each element. — Kevin Lee, Jan 18 '16 at 19:02

score 0 · Answer 2 · answered Jan 18 '16 at 18:40

0

Your problem is here:

 var value = items[type][i][value];

you should change it to

 var value = items[type][i].value;

answered Jan 18 '16 at 18:40

dovidweisz

1,215
13
24

Pushing to array

2 Answers2