push object array into array by index

Question

l know my question is similar for too many questions. l have checked all answers and all answers are not give me what l want exactly.

l have this array:

[
  {
    "size": true,
    "status": true,
    "desc": "صحن مخلمة",
    "name": "مخلمة",
    "id": "QmzeJgg2F2"
  }
]

l want to push new array object by index array above using this code:

  items_local: any[] = []; 

  add_addons(index,data) {

    this.items_local[index].addons.push(data.addons);

    console.log(this.items_local);
  }

expected output:

    [
  {
    "addons": [    // new array pushing
    {
      "price": 10
    },
    {
      "price": 10
    }
    ],
    "size": true,
    "status": true,
    "desc": "صحن مخلمة",
    "name": "مخلمة",
    "id": "QmzeJgg2F2"
  }
]

Error:

ERROR TypeError: Cannot read property 'push' of undefined

Answer 1

your original object doesn't have a addons key, hence you can't call the push property on it, first create that key and assign to empty array

  add_addons(index,data) {
    this.items_local[index].addons = []
    this.items_local[index].addons.push(data.addons);

    console.log(this.items_local);
  }