How to optimize this transformation from array to object with specific key?

Question

I have this array that inside has other arrays, and I wanted to turn this array into an array of objects. I would like to do this without using this index, and the object would like it to have these specific keys. I'm new to javascript and I would like to know if the way I did it was the best way, or if I can use a Map or Reduce to do what I want.

const listaCesar = [["cesar", "1", 1], ["thiago", "2", 2], ["giuseppe", "3", 3]]

const dict = []
listaCesar.forEach(item => dict.push({name: item[0], id: item[1], age: item[2]}))

console.log(dict)

This code works and gives me the expected result, but I don't know if I did it in the best way

ExpectResult = [{name: "cesar", id: "1", age: "1"}, {name: "thiago", id: "2", age: "2"}, {name: "giuseppe", id: "3", age: "3"}]

You are correct in your assumption that you could use .map(item => ({ ... })) instead. — Ma3x
– Ma3x, Commented Jun 23, 2022 at 14:29
@Ma3x no it can't be used, as property names required are different from values. — Code Maniac
– Code Maniac, Commented Jun 23, 2022 at 14:30
Using map() should yield similar performance. I would also use argument destructuring assignment. const dict = listaCesar.map(([name, id, age]) => ({ name, id, age })) — 3limin4t0r
– 3limin4t0r, Commented Jun 23, 2022 at 14:30
like this? listaCesar.map(item => dict.push({name: item[0], id: item[1], age: item[2]})) — Giuseppe Fantoni
– Giuseppe Fantoni, Commented Jun 23, 2022 at 14:31
@CodeManiac I meant what 3limin4t0r just posted above... map call and then either what OP did or with destructuring as suggested. — Ma3x
– Ma3x, Commented Jun 23, 2022 at 14:32

Prince Hernandez · Accepted Answer · 2022-06-23 14:32:34Z

your solution is not bad, but I think you want something more "Elegant" so you can reduce your function to something like this:

const dict = listaCesar.map(([name, id, age]) => ({ name, id, age }));

basically with [name, id, age] you are destructuring the inner array and using those same names in the object { name, id, age } you will create a key value object with those name as keys.

const listaCesar = [
  ["cesar", "1", 1],
  ["thiago", "2", 2],
  ["giuseppe", "3", 3]
]

const dict = []
listaCesar.forEach(item => dict.push({
  name: item[0],
  id: item[1],
  age: item[2]
}))

console.log(dict);

console.log('////////////////////////////////////////');

const dict2 = listaCesar.map(([name, id, age]) => ({
  name,
  id,
  age
}));
console.log(dict2);

if you want something more performant to avoid using another structure you can reuse the same array that you have following the same approach, in this case you do not return a new array instead you reuse the same index on the array to put your new object.

const listaCesar = [
  ["cesar", "1", 1],
  ["thiago", "2", 2],
  ["giuseppe", "3", 3]
]


listaCesar.forEach(([name, id, age], i) => {
  listaCesar[i] = {
    name,
    id,
    age
  }
})

console.log(listaCesar);

Code Maniac · Accepted Answer · 2022-06-23 14:30:55Z

0

One improvement you can do is use an array to keep names of properties and loop over it to create object, so that it becomes extensible

const listaCesar = [
  ["cesar", "1", 1],
  ["thiago", "2", 2],
  ["giuseppe", "3", 3]
]
const props = ['name', 'id', 'age', ]
const dict = listaCesar.map(item => props.reduce((a, b, i) => {
  a[b] = item[i]
  return a
}, {}))

console.log(dict)

answered Jun 23, 2022 at 14:30

Code Maniac

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