Object.entries

 const obj = { "un": 1, deux: 2, trois: 3 };

const tab = Object.entries(obj);

console.log(tab) // 

1. (3) [Array(2), Array(2), Array(2)]
1. 0: (2) ['un', 1]
2. 1: (2) ['deux', 2]
3. 2: (2) ['trois', 3]
4. length: 3
5. [[Prototype]]: Array(0)

const obj2 = Object.fromEntries(

  Object.entries(obj)

  .map(([ key, val ]) => [ `${key}*2`, val * 2 ])

);

console.log(obj2);

1. {un*2: 2, deux*2: 4, trois*2: 6}
1. deux*2: 4
2. trois*2: 6
3. un*2: 2

https://codepen.io/dupontcodepen/pen/abEaYeQ