How to change the nested object array by key value type in javascript

Question

I would like to know how modify array of objects in javascript.

i.e for obj change the value key array to string when value is array

change the value key string to array when value is string

also, how to convert output as input obj and (vice-versa-<input as output) in javascript

function newObject(obj){
  var result = obj.map(e=>typeof e.value === "string" ?
  {...e, value: [e.value] } :
   e.value.map(value => ({...e,value})) 
  ).flat()
  console.log(result);
  return result;

}

scenario1

input:
obj =[
 { id: 0, key: "s1", value: ["listA","listB"], img:"" },
 { id: 1, key: "s2", value: ["listC"], img: "" },
 { id: 2, key: "s3", value: ["listD","listE","listF"], img: "" }
]

Expected output:
[
  { id: 0, key: "s1", value: "listA,listB", img:""},
  { id: 1, key: "s2", value: "listC", img:""},
  { id: 2, key: "s3", value: "listD,listE,listF", img:""}
]

scenario 2

input
[
  { id: 0, key: "s1", value: "listA,listB", img:""},
  { id: 1, key: "s2", value: "listC", img:""},
  { id: 2, key: "s3", value: "listD,listE,listF", img:""}
]

Expected Output
[
 { id: 0, key: "s1", value: ["listA","listB"], img:"" },
 { id: 1, key: "s2", value: ["listC"], img: "" },
 { id: 2, key: "s3", value: ["listD","listE","listF"], img: "" }
]

What happened to listF in the last object of your output array? (first code block?) — Nick Parsons
– Nick Parsons, Commented Sep 4, 2020 at 12:05
@NickParsons thanks for reply, updated the code, was missed out — ved
– ved, Commented Sep 4, 2020 at 12:07
arr.forEach(item => item.value = item.value.join('') and arr.forEach(item => item.value = item.value.split(',') — user5734311
– user5734311, Commented Sep 4, 2020 at 12:09

Nick Parsons · Accepted Answer · 2020-09-04 12:15:36Z

When you use .map() you can return a new object with all the properties and values of the current object (...o), along with an update value property. The update value property will check if o.value is an array (checked using Array.isArray), if it is, it will .join() the elements into a string, it is a string (ie: not an array), it will .split() on the commas to convert the string into an array.

See example below:

function newObject(arr){
  return arr.map(o => ({
    ...o,
    value: Array.isArray(o.value) ? o.value.join() : o.value.split(',')
  }));
}

const arr1 = [ { id: 0, key: "s1", value: ["listA","listB"], img:"" }, { id: 1, key: "s2", value: ["listC"], img: "" }, { id: 2, key: "s3", value: ["listD","listE","listF"], img: "" } ];
const arr2 = [ { id: 0, key: "s1", value: "listA,listB", img:""}, { id: 1, key: "s2", value: "listC", img:""}, { id: 2, key: "s3", value: "listD,listE,listF", img:""} ];

const res1 = newObject(arr1);
const res2 = newObject(arr2);
console.log(res1);
console.log(res2);

maksymhlushek · Accepted Answer · 2020-09-04 13:59:37Z

2

we can use for loop to achieve more performance

let arr_1 = [
  { id: 0, key: "s1", value: ["listA","listB"], img:"" },
  { id: 1, key: "s2", value: ["listC"], img: "" },
  { id: 2, key: "s3", value: ["listD","listE","listF"], img: "" },

  { id: 0, key: "s1", value: "listA,listB", img:""},
  { id: 1, key: "s2", value: "listC", img:""},
  { id: 2, key: "s3", value: "listD,listE,listF", img:""}
]


const f = (arr) => {
  for(let i = 0; i < arr.length; i++) {
    let x = arr[i].value        
    arr[i].value = Array.isArray(x) ? x.join() : x.split(',')
  }
console.log(arr)
}

f(arr_1)

edited Sep 4, 2020 at 13:59

answered Sep 4, 2020 at 13:52

maksymhlushek

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