Angular5: Convert nested object to nested array for using in ngFor

Question

I have a nested object like this:

data =   [
        {
            "id": "0001",
            "type": "donut",
            "name": "Cake",
            "ppu": 0.55,
            "batters":
                {
                    "batter":
                        [
                            { "id": "1001", "type": "Regular" },
                            { "id": "1002", "type": "Chocolate" },
                            { "id": "1003", "type": "Blueberry" },
                            { "id": "1004", "type": "Devil's Food" }
                        ]
                },
            "topping":
                [
                    { "id": "5001", "type": "None" },
                    { "id": "5002", "type": "Glazed" },
                    { "id": "5005", "type": "Sugar" },
                    { "id": "5007", "type": "Powdered Sugar" },
                    { "id": "5006", "type": "Chocolate with Sprinkles" },
                    { "id": "5003", "type": "Chocolate" },
                    { "id": "5004", "type": "Maple" }
                ]
        },
        {
            "id": "0002",
            "type": "donut",
            "name": "Raised",
            "ppu": 0.55,
            "batters":
                {
                    "batter":
                        [
                            { "id": "1001", "type": "Regular" }
                        ]
                },
            "topping":
                [
                    { "id": "5001", "type": "None" },
                    { "id": "5002", "type": "Glazed" },
                    { "id": "5005", "type": "Sugar" },
                    { "id": "5003", "type": "Chocolate" },
                    { "id": "5004", "type": "Maple" }
                ]
        },
        {
            "id": "0003",
            "type": "donut",
            "name": "Old Fashioned",
            "ppu": 0.55,
            "batters":
                {
                    "batter":
                        [
                            { "id": "1001", "type": "Regular" },
                            { "id": "1002", "type": "Chocolate" }
                        ]
                },
            "topping":
                [
                    { "id": "5001", "type": "None" },
                    { "id": "5002", "type": "Glazed" },
                    { "id": "5003", "type": "Chocolate" },
                    { "id": "5004", "type": "Maple" }
                ]
        }
    ]

I would like to traverse through this object and display batter object data in my html using *ngFor but when i nest the *ngFor to achieve the same like this:

 <div *ngFor="let item of data">
       <!--Display first level elements here-->
       <div *ngFor="let batter of item.batters">
         <!--Display secondlevel elements here-->
       </div>
    </div>

i am getting the following error saying

Cannot find a differ supporting object '[object Object]' of type 'object'. NgFor only supports binding to Iterables such as Arrays.

How can i convert this nested object to nested array ? or is there a better way to flatten this Object using Typescript/EcmaScript/RxJS ?

Answer 1

It occurs, because you try to iterate object in loop, not array, look here:

"batters":{
      "batter":
          [
             { "id": "1001", "type": "Regular" }
           ]
},

This can be simplified, I believe to this output format:

"batters":[
   { "id": "1001", "type": "Regular" },
   { "id": "1002", "type": "Regular" }
]

It looks better and it will work in your case.

Simple:

let part = "batters":
                {
                    "batter":
                        []}

let extract = part["betters"]["batter"];

mainOrray["betters"] = extract;

Answer 2

After Edit: the json structure looks weird. To iterate trough batters it should be something like this I guess.

<div *ngFor="let item of data">
   <div *ngFor="let i of item.batters.batter">
      {{i.id}}, {{i.type}
   </div>
</div>