Spread operator to assign data inside array in an object

Question

I need to update the data inside the below state using spread operator. It has to be done such a way that data[0] should be updated with "vehOn":"Finance"

let state = {
  "data": [{
    "year": "2017",
    "make": "ALFA ROMEO",
    "model": "ILX 4D 2.0 PREMIUM PACKAGE"
  }],
  "error": ""
};

Modfied state should be like:

let modifiedstate = {
  "data": [{
    "year": "2017",
    "make": "ALFA ROMEO",
    "model": "ILX 4D 2.0 PREMIUM PACKAGE",
    "vehOn": "Finance"
  }],
  "error": ""
};

_"I need to ... using spread operator"_ - Why? Please format your question/code properly? And what have you tried so far? — Andreas, Dec 28 '18 at 15:29
@gaetanoM I am trying to get it done using the spread operator. — Jijil Kakkadathu, Dec 28 '18 at 15:37
@Andreas I have tried below implementation but didn't work as expected. :( let oldData = state.data[0]; let newData = {'vehOn':'finance'}; let mergedData = {... oldData, ...newData}; let mergedState1 = {...state.data, ...mergedData}; //Didn't work let mergedState2 = {...state, data:[...state.data,mergedData]}; //Didn't work — Jijil Kakkadathu, Dec 28 '18 at 15:44
But why do you need to use the spread operator? if your intention is to clone `state` you should know that the spread operator does not make shallow copies. — ApusApus, Dec 28 '18 at 15:46

score 1 · Accepted Answer · answered Dec 28 '18 at 15:55

As per documentation the only way I can see to achieve your result is:

let state = {
    "data": [{
        "year": "2017",
        "make": "ALFA ROMEO",
        "model": "ILX 4D 2.0 PREMIUM PACKAGE"
    }],
    "error": ""
};

let modifiedstate  = { "data": [{ ...state.data[0], ...{vehOn: "Finance"} }],
    "error": ""};

console.log(modifiedstate);

score 1 · Answer 2 · answered Dec 28 '18 at 16:04

const state = {
  "data": [{
    "year": "2017",
    "make": "ALFA ROMEO",
    "model": "ILX 4D 2.0 PREMIUM PACKAGE"
  }],
  "error": ""
};

console.log("---- state ----");
console.log(state);

const modifiedstate = { ...state,
  data: state.data.map((entry, i) => i === 0 ? ({ ...entry,
    vehOn: "Finance"
  }) : entry)
};

console.log("---- modifiedstate ----");
console.log(modifiedstate);

ApusApus · Answer 3 · 2018-12-28T16:01:17.200

0

If your intention is to create an object that is identical to state and you don't know what properties state can have you should look for a way to deep clone it

Otherwise if you are absolutely sure of the structure of state and want to do a simple clone you can do the following:

   let modifiedstate = "data": [{
     ...state.data[0],
     "vehOn": "Finance"
     }],
     "error": ""
   }

edited Dec 28 '18 at 16:01

answered Dec 28 '18 at 15:56

ApusApus

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Spread operator to assign data inside array in an object

3 Answers3