javascript map(val , index) , which condition val is variable and string

Question

After few research and test I'm still confuse about the map expression map((k,i) => { ... } )

Why my k is a string instead of variable when i create an object { k : arr[i] }

exemple 1

let name = 'test.val2'    
let test = ['name','ext'].map((k,i) => console.log({k :name.split('.')[i]}))

exemple 2

let name = 'test.val2'
let test = ['name','ext'].map((k,i) => console.log(k ,name.split('.')[i]))

exemple 3

let name = 'test.val2'
let test = ['name','ext'].map((k,i) => {
  let obj = {}
  obj[k] = name.split('.')[i]
  console.log(obj)
})