how can swap the key and array of values, of an object in JavaScript?-CodePudding

This is my data:

obj = Object {
  Great Lakes: Array(3) ["Michigan", "Indiana", "Ohio"]
  Heartland: Array(2) ["Missouri", "Illinois"]
}

How can I change it to something like one by one:

{"Illinois": "Heartland", "Michigan": "Great Lakes", ...}

I have to use Map, Object.entries and Array.flat().

I used : namemap = new Map(Object.entries(obj).map(function ([k, v]) {return [v, k];} )) but this is not I want or maybe this is not complete.

CodePudding user response：

Using map can do it,but first we need to make sure that we can access the array value correctly.

let data = {
  'Great Lakes':["Michigan", "Indiana", "Ohio"],
  'Heartland': ["Missouri", "Illinois"]
}

let result = {}
Object.keys(data).map(d1 => data[d1].forEach(d2 => result[d2] = d1))
console.log(result)

CodePudding user response：

Your code is almost correct, you just need to iterate the values in each array in obj:

const obj = {
  'Great Lakes': ["Michigan", "Indiana", "Ohio"],
  'Heartland': ["Missouri", "Illinois"]
}

const namemap = new Map(
  Object.entries(obj)
    .map(([k, a]) => a.map(v => [v, k]))
    .flat()
)

for (const [key, value] of namemap.entries()) {
  console.log(`${key} : ${value}`);
}